What do white blood cells do with FOREIGN white blood cells?

What do white blood cells do with FOREIGN white blood cells?

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White blood cells or leukocytes are known to fight invaders, infections or basically anything foreign. They also contain DNA (while red blood cells don't). But what about foreign "white blood cells" received in a transfusion or sexual intercourse (as semen, not sperm, holds "lymphocytes" which are a type of white blood cells, they can "possibly" enter the blood circulation, not quite sure).

Anyways, my question is:

1) Do white blood cells "fight" the foreign white blood cells and kill them off? OR is that something cleaned by the spleen itself? (considering WBC lifespan is 13-20 days so they die off their own). So do they "get" attacked by the host's WBC or do they naturally die off their own?

2) Does the body detect them as "foreign"?

3) I've also heard about the "extracellular DNA" phenomenon. Which is, the ability of DNA to exit a cell (while it's dying) and float in the extracellular (non-cellular) environment. The DNA is degraded during a cell death but it can definitely exit a cell and float non-cellular in the environment. This is also true for the cell's RNA. This is labelled as an "extraceullar DNA/RNA" or a DNA/RNA without a cell. So that being said, can the DNA of foreign leukocytes or white blood cells that do not belong to the host (having a completely different DNA, of course) exit it's cell during it's death and become extracellular DNA? Is that even remotely possible? Also, can that extracellular DNA (keep in mind, the DNA is a fairly stable molecule) ever remain in the circulation or the human body for life? Perhaps in the bloodstream? or in one of the organs? or in a biofilm? (considering exDNA is a component of a biofilm) Does that even have the "slightest" possibiliy of happening? For it to remain there for life?

1) If it is, wouldn't the body (the immune system or WBC) ever "react" or "act" on eliminating the "foreign DNA" of another person that's floating around? Or is that something which will remain for life OR be eventually faded away? I'm well aware of enzymes such as DNAses/RNAses (enzymes responsible for DNA and RNA degradation) but do they do that in the blood? And that being said, "sometimes" in a biolfilm they don't.

2) And even if it gets stuck in a "biofilm" (assuming it's possible?), would it "EVER" degrade eventually or remain there for life? OR CAN/WILL the "biofilm" holding such extracellular components degrade eventually or will it remain for life as well? (can they remain there forever?).

3) A simple way to explain this would be if I insert hundreds of "foreign DNA" (strands, not cells) into your blood stream, what would happen to them?

4) Can it get "stuck" or get glued to an organ or it's cells and remain there for life somewhere out in the deep where they won't be found? Since I'm not an expert in molecular biology I don't understand. In other words, can it EVER remain there for life with "ANY" slightest 1% possibility with all the possibilities I've explained or any other possibility of it remaining there for life? And same goes for the RNA. Having someone else's DNA and RNA scares the shit outta me. And having that for the rest of my life, makes me really uncomfortable.

My question is for both the DNA and the RNA.

I don't want "assumptions" or hypothesis please. Please answer if you're an expert in microbiology/molecular biology, others, etc. And are well aware of what I'm talking about. I will greatly appreciate it.

Also, this is a tricky one! (I completely don't understand this)

The molecules secreted by these "foreign" white blood cells after their death would provide structural and biochemical support to other cells so wouldn't a part of his trace (his molecules) would remain in other cells forever once they consume it? Or the molecules get replaced on a cellular level itself if I'm not mistaken? Wouldn't his molecules be a part of my body forever?

Please answer if you're an expert in microbiology/molecular biology, others, etc. And are well aware of what I'm talking about. I will greatly appreciate it. I don't want assumptions or hypothesis only whatever is known, proven, researched & concluded as a fact. :)

Thanks guys,


Okay, you have a lot of questions there. I'll try to give some answers, but if you want more details or background knowledge I'd recommend you to read /study more about immunology (none of your questions are actually about molecular biology or cell biology).

2) Foreign cells are generally recognised by the immune system, based on the HLA molecules on the cells: all cells that do not have the exact same HLA molcules are recognised as forgein and attack by the immune system (cells without HLA are not human and by 'default' foreign). Since there are many different variants of the HLA class I gene and humans have usually 6 different ones, its very unlikely that a cell from someone else would not be attacked (that's why it's so hard to find matching organ donors).

1) Foreign cells are attacked by the immune system, the spleen's purpose is to remove/recycle old blood cells from the body itself. Depending on how the immune system recognises a cell (e.g. by antibodies or diretcly by immune cells) different strategies to fight the foreign cell are activated.

3) There are certain receptors on some immune cells that can recognise extra-cellular DNA or RNA. This recognition is not sequence specific und usually causes an inflammatory reaction, because extra cellular DNA is a sign of either cell damage (by necrosis) or invading pathogens. After the immune system recognised such 'invading' factors they are usually taken up and removed by macrophages.

Generally speaking all of this only happens if foreign cells or DNA manages to get into your body (e.g. if you would inject it). It's very unlikely that DNA or cells can pass into your body unless you have open wounds. (White blood cells usually only are able to pass the endothelium of blood vessels, not other kind of barriers)

White Blood Cells Are Picky About Sugar

Biology textbooks are blunt--neutrophils are mindless killers. These white blood cells patrol the body and guard against infection by bacteria and fungi, identifying and destroying any invaders that cross their path. But new evidence, which may lead to better drugs to fight deadly pathogens, indicates that neutrophils might actually distinguish among their targets.

A scientist in the lab of Whitehead Member Gerald Fink has discovered that neutrophils recognize and respond to a specific form of sugar called beta-1,6-glucan on the surface of fungi. This sugar comprises just a small fraction of the fungal cell wall, much less than another sugar with a slightly different chemical conformation called beta-1,3-glucan. Because the scarce form of the sugar elicits a much stronger reaction from immune cells than the abundant one, it appears that neutrophils can distinguish between two nearly identical chemicals.

"These results show that engulfment and killing by neutrophils varies, depending on cell wall properties of the microbe," explains Whitehead postdoctoral researcher Ifat Rubin-Bejerano, first author on the paper, which appears July 11 in the journal Cell Host & Microbe. "We showed that neutrophils respond in a completely different way to slight changes in sugar composition. If we are able to use this unique sugar to excite the immune system, it may help the human body fight infection."

"Previously, everyone thought that these key cells of the immune system weren't picky and would eat anything that looked foreign," adds Fink, who is also an MIT professor of biology. "Ifat's work has shown that the cells aren't little Pac-Men, but can discriminate one pathogen from another."

Rubin-Bejerano had evidence that neutrophils respond to beta-glucan. After coating tiny beads with a variety of substances (including beta-1,3-glucan and beta-1,6-glucan), she exposed them to the neutrophils and was surprised to see a striking difference in their response to the two sugars. The neutrophils quickly engulfed many of the beads coated with beta-1,6-glucan, but only a few of those covered in beta-1,3-glucan.

Previous studies indicated that blood serum (basically blood minus cells) helps neutrophils recognize their enemies, so Rubin-Bejerano decided to look for clues to their response in this mixture. She identified several proteins in serum that bind to beta-1,6-glucan, but not beta-1,3-glucan, and then pinpointed a molecule on the surface of the neutrophil that recognizes these proteins.

To link her experiments back to real fungi, Rubin-Bejerano worked with the pathogen Candida albicans, which is the most common fungus in blood stream infections. She used an enzyme to digest beta-1,6-glucan from the fungal cell wall, leaving the beta-1,3-glucan intact. She then unleashed the neutrophils on these altered cells and observed a 50 percent reduction in the immune response.

Our bodies maintain a fine balance between the immune system and microbes. Antibiotics and antifungals tilt the balance in favor of the immune system by targeting the microbes directly. A substance like beta-1,6-glucan could help tilt this balance further by stimulating immune cells.

Rubin-Bejerano's work offers hope for combating the growing problem of microbial infections, which can seriously threaten human health--particularly in patients with compromised immune systems. In fact, Rubin-Bejerano co-founded a company called ImmuneXcite to explore this possibility.

Not an invincible defense…

Despite the amazing ability to protect your body, the immune system is not foolproof.Not only can certain viruses outwit your immune system's defenses, but genetic malfunctions can result in an ineffective immune system.

The Human Immunodeficiency Virus (HIV), infects the CD4+ T-cells, a type of lymphocyte, causing the cells to die. If enough cells are killed, the immune system no longer functions and the person becomes susceptible to many different diseases.

An example of a genetic disease of the immune system is lupus which causes your immune system to mistakenly attack your body’s healthy cells.

Exposure to certain toxic chemicals can also affect your immune system. The study of substances that harm the immune system is called immunotoxicology (immuno: related to the immune system, toxicology: the study of harmful substances).

After exposure to an immunotoxicant, a chemical that harms the immune system, your body may not be able to produce the variety or number of defense cells that it needs to protect itself.

If the immune system is damaged, it cannot attack foreign cells such as viruses, bacteria or tumor cells that can cause health problems.

How Do White Blood Cells Fight Infections?

White blood cells help to recognize when a foreign and potentially harmful pathogen enters the body, and they respond by releasing antibodies, such as lymphocytes and phagocytes, which attach to the pathogen and work to eradicate it. A high amount of white blood cells are found in the lymph nodes, which is why a symptom or sign of infection in the body can be evident by swollen lymph nodes.

Depending on the nature of the pathogen that enters the body, the body's white blood cells can respond in various ways to fight it.

Some cell-damaging bacteria release toxins into the body. They do so by latching onto host cells to destroy them. This negative process can be accomplish by the bacteria either consuming the host cell's nutrients, releasing toxins into the cell, simply destroying the structure of the cell or causing the body to have a hypersensitive reaction. White blood cells can release anti-toxins to counteract the effects of this bad bacteria.

A particular type of white blood cell, referred to as a phagocyte, is responsible for consuming the pathogens found in the body. They can also consume and digest pathogens that have been destroyed by other white blood cells.

Lymphocytes release antibodies that help to either destroy pathogens or make it easier for the phagocyte to do its job in digesting the pathogen.

White Blood Cells

White blood cells, also called leukocytes (leuko = white), make up approximately one percent by volume of the cells in blood. The role of white blood cells is very different than that of red blood cells: they are primarily involved in the immune response to identify and target pathogens, such as invading bacteria, viruses, and other foreign organisms. White blood cells are formed continually some only live for hours or days, but some live for years.

The morphology of white blood cells differs significantly from red blood cells. They have nuclei and do not contain hemoglobin. The different types of white blood cells are identified by their microscopic appearance after histologic staining, and each has a different specialized function. The two main groups, both illustrated in the figure below are the granulocytes, which include the neutrophils, eosinophils, and basophils, and the agranulocytes, which include the monocytes and lymphocytes.

(a) Granulocytes—including neutrophils, eosinophils and basophils—are characterized by a lobed nucleus and granular inclusions in the cytoplasm. Granulocytes are typically first-responders during injury or infection. (b) Agranulocytes include lymphocytes and monocytes. Lymphocytes, including B and T cells, are responsible for adaptive immune response. Monocytes differentiate into macrophages and dendritic cells, which in turn respond to infection or injury.

Granulocytes contain granules in their cytoplasm the agranulocytes are so named because of the lack of granules in their cytoplasm. Some leukocytes become macrophages that either stay at the same site or move through the blood stream and gather at sites of infection or inflammation where they are attracted by chemical signals from foreign particles and damaged cells. Lymphocytes are the primary cells of the immune system and include B cells, T cells, and natural killer cells. B cells destroy bacteria and inactivate their toxins. They also produce antibodies. T cells attack viruses, fungi, some bacteria, transplanted cells, and cancer cells. T cells attack viruses by releasing toxins that kill the viruses. Natural killer cells attack a variety of infectious microbes and certain tumor cells.

One reason that HIV poses significant management challenges is because the virus directly targets T cells by gaining entry through a receptor. Once inside the cell, HIV then multiplies using the T cell’s own genetic machinery. After the HIV virus replicates, it is transmitted directly from the infected T cell to macrophages. The presence of HIV can remain unrecognized for an extensive period of time before full disease symptoms develop.

T Cells

Like B cells, T cells are also lymphocytes. T cells are produced in bone marrow and travel to the thymus where they mature. T cells actively destroy infected cells and signal other immune cells to participate in the immune response. T cell types include:

  • Cytotoxic T cells: actively destroy cells that have become infected
  • Helper T cells: assist in the production of antibodies by B cells and help activate cytotoxic T cells and macrophages
  • Regulatory T cells: suppress B and T cell responses to antigens so an immune response does not last longer than necessary
  • Natural Killer T (NKT) cells: distinguish infected or cancerous cells from normal body cells and attack cells that are not identified as body cells
  • Memory T cells: help to quickly identify previously encountered antigens for a more effective immune response

Reduced numbers of T cells in the body can seriously compromise the ability of the immune system to perform its defensive functions. This is the case with infections such as HIV. In addition, defective T cells may lead to the development of different types of cancer or autoimmune diseases.

What Are White Blood Cells

Your blood is made up of white blood cells, red blood cells, plasma, and platelets. White blood cells account for about 1% of your blood but they have an enormous impact. White blood cells (WBCs) are also known as leukocytes or white corpuscles. They protect your body against illness and disease.

Red blood cells and most white blood cells are made in your bone marrow, the soft fatty tissue in your bone cavities. They are then stored in your blood and lymph tissues. Some white blood cells only survive for one to three days, so your bone marrow is constantly producing them.

Think of white blood cells as your immunity cells who are constantly at war. They move within your bloodstream and work with your immune system to fight infections, bacteria, and any other foreign invaders that could affect your health.

Whenever your body is in distress or under attack from infection, your white blood cells rush in to defend your health. They help to destroy harmful substances and prevent illness.

There are different types of white blood cells that all serve a slightly different purpose.

Some types of white blood cells are:

  • Eosinophils - they help with allergic responses as well as attack and kill parasites and cancer cells.
  • Basophils - produce histamine during an allergic reaction
  • Neutrophils - fight infection by killing and digesting bacteria and fungi
  • Monocytes - help to break down bacteria

What Causes White Blood Cells to Be Low?

If your white blood cell count is slightly low, it may be a result of fatigue and stress. Typically, your body will resolve this on its own after some much-needed rest and nutrition. Your doctor may repeat a blood test just to be sure though.

When white blood cell count is too low it can no longer fight infection. This can result in a condition known as leukopenia . There are different types of leukopenia depending on which type of white blood cell you’re low in. For example, if your blood is low in neutrophils, the type of leukopenia is known as neutropenia. Neutrophils are the white blood cells that protect you from bacteria and fungal infections.

Other conditions may produce a low white blood cell count. You may be on some medications or radiation therapy that can lower your amount of white blood cells. Your doctor will be monitoring you in those instances already.

A drastic result in low white blood count can be related to additional diseases such as cancer, liver disease, lupus, autoimmune disorders, HIV, lupus, and additional infections within your body.

Not every low white blood cell count is related to these diseases however, diseases are not to be excluded, and depending on the low range of your results, doctors will lead you in the right direction.

A drop in white blood cell count can also be as a result of the following:

  • Viral infections
  • Alcohol abuse
  • Poor nutrition
  • Medications like antibiotics
  • Autoimmune disorders
  • Congenital diseases

When you have a low white blood cell count, you may notice signs of infection like a high fever, chills, and sweating. If your white blood cell is low due to infection, you may also notice a sore throat, cough, and shortness of breath.

How Can I Improve My White Blood Cells Naturally?

There are a few natural ways to boost your white blood cells such as:

  • If you are overweight, losing a few pounds can help increase your immunity.
  • Drinking water is proven to increase immunity by flushing out toxins.
  • Decreasing sugars and unhealthy fats also can boost your immune system by keeping those white blood cells healthy.
  • Sleep is another key factor to increase your white blood cells naturally. So, find your Zen, reduce your stress, and get enough zzzzs.

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White Blood Cells

There are far fewer white blood cells in blood than there are red blood cells the white blood cells make up only about 1 percent of blood. Their functions are vastly different from each other as well. White blood cells are also called leukocytes.

The chief function of white blood cells is that of defense against disease. They are essential to human health. Any time a person falls ill, the various kinds of white blood cells rush to assist in attacking the invading pathogen.

Another interesting function of white blood cells is that they actually consume dead cells, tissues and aging red blood cells.

How To Increase White Blood Cell Count Naturally

  • In addition to eating, there are daily habits that we must take into account when increasing the white blood cell count :
  • Daily exercise: approximately 30 minutes, this allows the white blood cells and antibodies to move much faster throughout the body.
  • Avoid stressful situations: this being the main trigger for most diseases, you should try to avoid it by trying to handle situations with calm and relaxation.
  • Increase your water intake: at least 12 glasses of water a day to boost the immune system.
  • Relaxation therapies: for at least 15 minutes a day you should practice deep breathing exercise.
  • Avoid sedentary lifestyle: it is not essential to maintain a daily intense exercise routine, however, it is recommended to be active at all times, such as walking or jogging to increase adrenaline and also the body’s defences.
  • Rest as long as necessary: this will be vital to regain energy and boost the immune system.


The name "white blood cell" derives from the physical appearance of a blood sample after centrifugation. White cells are found in the buffy coat, a thin, typically white layer of nucleated cells between the sedimented red blood cells and the blood plasma. The scientific term leukocyte directly reflects its description. It is derived from the Greek roots leuk- meaning "white" and cyt- meaning "cell". The buffy coat may sometimes be green if there are large amounts of neutrophils in the sample, due to the heme-containing enzyme myeloperoxidase that they produce.


All white blood cells are nucleated, which distinguishes them from the anucleated red blood cells and platelets. Types of leukocytes can be classified in standard ways. Two pairs of broadest categories classify them either by structure (granulocytes or agranulocytes) or by cell lineage (myeloid cells or lymphoid cells). These broadest categories can be further divided into the five main types: neutrophils, eosinophils, basophils, lymphocytes, and monocytes. [2] These types are distinguished by their physical and functional characteristics. Monocytes and neutrophils are phagocytic. Further subtypes can be classified.

Granulocytes are distinguished from agranulocytes by their nucleus shape (lobed versus round, that is, polymorphonuclear versus mononuclear) and by their cytoplasm granules (present or absent, or more precisely, visible on light microscopy or not thus visible). The other dichotomy is by lineage: Myeloid cells (neutrophils, monocytes, eosinophils and basophils) are distinguished from lymphoid cells (lymphocytes) by hematopoietic lineage (cellular differentiation lineage). [6] Lymphocytes can be further classified as T cells, B cells, and natural killer cells.

    : releases antibodies and assists activation of T cells :
      + Th (T helper) cells: activate and regulate T and B cells + cytotoxic T cells: virus-infected and tumor cells. : bridge between innate and adaptive immune responses phagocytosis : Returns the functioning of the immune system to normal operation after infection prevents autoimmunity


    Neutrophils are the most abundant white blood cell, constituting 60-70% of the circulating leukocytes, [4] and including two functionally unequal subpopulations: neutrophil-killers and neutrophil-cagers. They defend against bacterial or fungal infection. They are usually first responders to microbial infection their activity and death in large numbers form pus. They are commonly referred to as polymorphonuclear (PMN) leukocytes, although, in the technical sense, PMN refers to all granulocytes. They have a multi-lobed nucleus, which consists of three to five lobes connected by slender strands. [9] This gives the neutrophils the appearance of having multiple nuclei, hence the name polymorphonuclear leukocyte. The cytoplasm may look transparent because of fine granules that are pale lilac when stained. Neutrophils are active in phagocytosing bacteria and are present in large amount in the pus of wounds. These cells are not able to renew their lysosomes (used in digesting microbes) and die after having phagocytosed a few pathogens. [10] Neutrophils are the most common cell type seen in the early stages of acute inflammation. The average lifespan of inactivated human neutrophils in the circulation has been reported by different approaches to be between 5 and 135 hours. [11] [12]


    Eosinophils compose about 2-4% of the WBC total. This count fluctuates throughout the day, seasonally, and during menstruation. It rises in response to allergies, parasitic infections, collagen diseases, and disease of the spleen and central nervous system. They are rare in the blood, but numerous in the mucous membranes of the respiratory, digestive, and lower urinary tracts. [9]

    They primarily deal with parasitic infections. Eosinophils are also the predominant inflammatory cells in allergic reactions. The most important causes of eosinophilia include allergies such as asthma, hay fever, and hives and also parasitic infections. They secrete chemicals that destroy these large parasites, such as hookworms and tapeworms, that are too big for any one WBC to phagocytize. In general, their nucleus is bi-lobed. The lobes are connected by a thin strand. [9] The cytoplasm is full of granules that assume a characteristic pink-orange color with eosin staining.


    Basophils are chiefly responsible for allergic and antigen response by releasing the chemical histamine causing the dilation of blood vessels. Because they are the rarest of the white blood cells (less than 0.5% of the total count) and share physicochemical properties with other blood cells, they are difficult to study. [13] They can be recognized by several coarse, dark violet granules, giving them a blue hue. The nucleus is bi- or tri-lobed, but it is hard to see because of the number of coarse granules that hide it.

    They excrete two chemicals that aid in the body's defenses: histamine and heparin. Histamine is responsible for widening blood vessels and increasing the flow of blood to injured tissue. It also makes blood vessels more permeable so neutrophils and clotting proteins can get into connective tissue more easily. Heparin is an anticoagulant that inhibits blood clotting and promotes the movement of white blood cells into an area. Basophils can also release chemical signals that attract eosinophils and neutrophils to an infection site. [9]


    Lymphocytes are much more common in the lymphatic system than in blood. Lymphocytes are distinguished by having a deeply staining nucleus that may be eccentric in location, and a relatively small amount of cytoplasm. Lymphocytes include:

      make antibodies that can bind to pathogens, block pathogen invasion, activate the complement system, and enhance pathogen destruction. :
        + helper T cells: T cells displaying co-receptorCD4 are known as CD4+ T cells. These cells have T-cell receptors and CD4 molecules that, in combination, bind antigenic peptides presented on major histocompatibility complex (MHC) class II molecules on antigen-presenting cells. Helper T cells make cytokines and perform other functions that help coordinate the immune response. In HIV infection, these T cells are the main index to identify the individual's immune system integrity. + cytotoxic T cells: T cells displaying co-receptor CD8 are known as CD8+ T cells. These cells bind antigens presented on MHC I complex of virus-infected or tumour cells and kill them. Nearly all nucleated cells display MHC I. possess an alternative T cell receptor (different from the αβ TCR found on conventional CD4+ and CD8+ T cells). Found in tissue more commonly than in blood, γδ T cells share characteristics of helper T cells, cytotoxic T cells, and natural killer cells.


      Monocytes, the largest type of WBCs, share the "vacuum cleaner" (phagocytosis) function of neutrophils, but are much longer lived as they have an extra role: they present pieces of pathogens to T cells so that the pathogens may be recognized again and killed. This causes an antibody response to be mounted. Monocytes eventually leave the bloodstream and become tissue macrophages, which remove dead cell debris as well as attack microorganisms. Neither dead cell debris nor attacking microorganisms can be dealt with effectively by the neutrophils. Unlike neutrophils, monocytes are able to replace their lysosomal contents and are thought to have a much longer active life. They have the kidney-shaped nucleus and are typically agranulated. They also possess abundant cytoplasm.

      Some leucocytes migrate into the tissues of the body to take up a permanent residence at that location rather than remaining in the blood. Often these cells have specific names depending upon which tissue they settle in, such as fixed macrophages in the liver, which become known as Kupffer cells. These cells still serve a role in the immune system.

      The two commonly used categories of white blood cell disorders divide them quantitatively into those causing excessive numbers (proliferative disorders) and those causing insufficient numbers (leukopenias). [14] Leukocytosis is usually healthy (e.g., fighting an infection), but it also may be dysfunctionally proliferative. WBC proliferative disorders can be classed as myeloproliferative and lymphoproliferative. Some are autoimmune, but many are neoplastic.

      Another way to categorize disorders of white blood cells is qualitatively. There are various disorders in which the number of white blood cells is normal but the cells do not function normally. [15]

      Neoplasia of WBCs can be benign but is often malignant. Of the various tumors of the blood and lymph, cancers of WBCs can be broadly classified as leukemias and lymphomas, although those categories overlap and are often grouped as a pair.


      A range of disorders can cause decreases in white blood cells. This type of white blood cell decreased is usually the neutrophil. In this case the decrease may be called neutropenia or granulocytopenia. Less commonly, a decrease in lymphocytes (called lymphocytopenia or lymphopenia) may be seen. [14]


      Neutropenia can be acquired or intrinsic. [16] A decrease in levels of neutrophils on lab tests is due to either decreased production of neutrophils or increased removal from the blood. [14] The following list of causes is not complete.

      • Medications - chemotherapy, sulfas or other antibiotics, phenothiazenes, benzodiazepines, antithyroids, anticonvulsants, quinine, quinidine, indomethacin, procainamide, thiazides
      • Radiation
      • Toxins - alcohol, benzenes
      • Intrinsic disorders - Fanconi's, Kostmann's, cyclic neutropenia, Chédiak–Higashi
      • Immune dysfunction - disorders of collagen, AIDS, rheumatoid arthritis
      • Blood cell dysfunction - megaloblastic anemia, myelodysplasia, marrow failure, marrow replacement, acute leukemia
      • Any major infection
      • Miscellaneous - starvation, hypersplenism

      Symptoms of neutropenia are associated with the underlying cause of the decrease in neutrophils. For example, the most common cause of acquired neutropenia is drug-induced, so an individual may have symptoms of medication overdose or toxicity. Treatment is also aimed at the underlying cause of the neutropenia. [17] One severe consequence of neutropenia is that it can increase the risk of infection. [15]


      Defined as total lymphocyte count below 1.0x10 9 /L, the cells most commonly affected are CD4+ T cells. Like neutropenia, lymphocytopenia may be acquired or intrinsic and there are many causes. [15] This is not a complete list.

      • Inherited immune deficiency - severe combined immunodeficiency, common variable immune deficiency, ataxia-telangiectasia, Wiskott–Aldrich syndrome, immunodeficiency with short-limbed dwarfism, immunodeficiency with thymoma, purine nucleoside phosphorylase deficiency, genetic polymorphism
      • Blood cell dysfunction - aplastic anemia
      • Infectious diseases - viral (AIDS, SARS, West Nile encephalitis, hepatitis, herpes, measles, others), bacterial (TB, typhoid, pneumonia, rickettsiosis, ehrlichiosis, sepsis), parasitic (acute phase of malaria)
      • Medications - chemotherapy (antilymphocyte globulin therapy, alemtuzumab, glucocorticoids)
      • Radiation
      • Major surgery
      • Miscellaneous - ECMO, kidney or bone marrow transplant, hemodialysis, kidney failure, severe burns, celiac disease, severe acute pancreatitis, sarcoidosis, protein-losing enteropathy, strenuous exercise, carcinoma
      • Immune dysfunction - arthritis, systemic lupus erythematosus, Sjögren syndrome, myasthenia gravis, systemic vasculitis, Behcet-like syndrome, dermatomyositis, granulomatosis with polyangiitis
      • Nutritional/Dietary - alcohol use disorder, zinc deficiency

      Like neutropenia, symptoms and treatment of lymphocytopenia are directed at the underlying cause of the change in cell counts.

      Proliferative disorders

      An increase in the number of white blood cells in circulation is called leukocytosis. [14] This increase is most commonly caused by inflammation. [14] There are four major causes: increase of production in bone marrow, increased release from storage in bone marrow, decreased attachment to veins and arteries, decreased uptake by tissues. [14] Leukocytosis may affect one or more cell lines and can be neutrophilic, eosinophilic, basophilic, monocytosis, or lymphocytosis.


      Neutrophilia is an increase in the absolute neutrophil count in the peripheral circulation. Normal blood values vary by age. [15] Neutrophilia can be caused by a direct problem with blood cells (primary disease). It can also occur as a consequence of an underlying disease (secondary). Most cases of neutrophilia are secondary to inflammation. [17]

      • Conditions with normally functioning neutrophils – hereditary neutrophilia, chronic idiopathic neutrophilia (chronic myelogenous (CML)) and other myeloproliferative disorders[18]


      A normal eosinophil count is considered to be less than 0.65 × 10 9 /L. [15] Eosinophil counts are higher in newborns and vary with age, time (lower in the morning and higher at night), exercise, environment, and exposure to allergens. [15] Eosinophilia is never a normal lab finding. Efforts should always be made to discover the underlying cause, though the cause may not always be found. [15]

      The complete blood cell count is a blood panel that includes the overall WBC count and the white blood cell differential, a count of each type of white blood cell. Reference ranges for blood tests specify the typical counts in healthy people.

      TLC- (Total leucocyte count): Normal TLC in an adult person is 6000–8000 WBC/mm^3 of blood.

      DLC- (Differential leucocyte count): Number/ (%) of different types of leucocytes per cubic mm. of blood.

      Below are blood reference ranges for various types leucocytes/WBCs. [19]

      WBC Formation

      Haematopoiesis refers to the formation of blood cells components. It is necessary for vertebrate function.

      Learning Objectives

      Describe the formation of leukocytes (white blood cells, or WBCs)

      Key Takeaways

      Key Points

      • Haematopoietic stem cells are self-renewing and reside in the medulla of the bone ( bone marrow ).
      • All blood cells are divided into two main lineages, produced through lymphoid progenitor cells or myeloid progenitor cells depending on lineage type.
      • Lymphoid progenitor cells differentiate into B and T cells and NK cells.
      • Myeloid progenitor cells differentiate into myelocytes (granulocytes and monocytes) or non-leukocytes such as erythorocytes and megakaryocytes (which produce platelets).
      • Before birth, most blood cell formation occurs in the liver or spleen, which tend to enlarge when used for hematopoiesis. In adults, most blood production occurs in the bone marrow.

      Key Terms

      • myelocyte: A large cell found in bone marrow that becomes a granulocyte or monocyte when mature.
      • differentiation: The gradual changes that occur when a cell or tissue type changes into a different type. Cells generally become more specialized the more they differentiate, and are considered to be terminally differentiated when they cannot differentiate (and often cannot divide) any further.
      • megakaryocyte: A large cell found in bone marrow, responsible for the production of platelets.

      Haematopoiesis refers to the formation of blood cellular components, including both white and red blood cells. All cellular blood components are derived from haematopoietic stem cells located within the bone marrow. In a healthy adult, approximately 10 11 –10 12 new blood cells are produced daily to maintain equilibrium levels in peripheral circulation.

      Leukocyte Haematopoiesis

      Haematopoietic stem cells (HSCs) reside in the bone marrow and have the unique ability to give rise to all mature blood cell types through differentiation into other progenitor cells. HSCs are self-renewing. When they proliferate, at least some daughter cells remain HSCs, so the pool of stem cells does not become depleted over time. The daughters are the myeloid and lymphoid progenitor cells, which cannot self renew but differentiate into various myeloid leukocytes and lymphocytes respectively. This is one of the body’s vital processes.

      Leukocyte Lineages

      Two different leukocyte lineages and two non-leukocyte lineages arise from the progeny of HSCs. Following this split in differentiation, the subtypes undergo eventual differentiation into terminally-differentiated leukocytes, which typically do not divide independently.

      1. The lymphocyte lineage derives from common lymphoid progenitor cells, which in turn become lymphoblasts before differentiating into T cells, B cells, and NK cells.
      2. Myelocytes are an offshoot of common myeloid progenitor cells, which also differentiate into the erythropoietic and magakaryotic progenitors. This diverse group differentiates into granulocytes and monocytes. Monocytes further differentiate into macrophages or dendritic cells upon reaching certain tissues.
      3. Megakaryocytes (the cells that produce platelets) and erythrocytes (red blood cells) are not formally considered to be leukocytes, but arise from the common myeloid progenitor cells that produce the other cellular components of blood.

      Hematopoiesis in Humans: This diagram shows hematopoiesis as it occurs in humans.

      Sites of Haematopoesis in Pre- and Postnatal Periods

      In developing embryos, blood formation occurs in aggregates of blood cells in the yolk sac called blood islands. However, most of blood supply comes from the mother through the placenta. As development progresses, blood formation occurs primarily in the spleen, liver, and lymph nodes.

      When bone marrow develops, it eventually assumes the task of forming most of the blood cells for the entire organism. However, maturation, activation, and some proliferation of lymphoid cells occurs in lymphoid organs (spleen, thymus, and lymph nodes). In children, haematopoiesis occurs in the marrow of the long bones such as the femur and tibia. In adults, it occurs mainly in the pelvis, cranium, vertebrae, and sternum.

      In some cases, the liver, thymus, and spleen may resume their haematopoietic function if necessary. This is called extramedullary haematopoiesis. It may cause these organs to hypertrophy and increase in size substantially. During fetal development, the liver functions as the main haematopoetic organ since bones and marrow develop later. Therefore, the liver is enlarged during development relative to its mature proportions.

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