White Blood Cells (Leukocytes)
Posted: Saturday, August 20th, 2022 | Updated: Tuesday, March 26th, 2024
Posted: Saturday, August 20th, 2022 | Updated: Tuesday, March 26th, 2024
An Overview of White Blood Cells
White blood cells function as a mechanism of defense for the body. There are five types of white blood cells; neutrophils, basophils, eosinophils, monocytes, and lymphocytes. Neutrophils, basophils, eosinophils, and monocytes perform phagocytosis as their defense mechanism while lymphocytes aide in the production of antibodies and cellular immunity. Neutrophils, basophils, and eosinophils have a multilobed and segmented nucleus. Eosinophils often have a two lobed nucleus and basophils have a two to three lobed nucleus. Lymphocytes have a single round shaped nucleus and monocytes have a nucleus without segments that may vary in it's shape. Neutrophils, basophils, and eosinophils all have cytoplasmic granules that may pick up stain while lymphocytes and monocytes do not. Neutrophil cytoplasmic granules are usually not visible. Basophil cytoplasmic granules stain blue and eosinophil's stain red
Neutrophils
The role of a neutrophil is to perform phagocytosis primarily in the body tissues. The cytoplasmic granules of the neutrophil contain lysosomal enzymes which help to kill any invading microorganisms that may cause disease or harm to the body. Neutrophils are transported by blood to their site of action. Right shift neutrophilia is characterized as an increase in mature or segmented neutrophils. This is usually seen in cases related to stress, fear, excitement, exercise, hyperadrenocorticism, or corticosteroid use. Hypersegmentation of neutrophils with greater than five nuclear lobes may be caused by prolonged corticosteroid use, vitamin B12 deficiency, and/or folate deficiencies. Left shift neutrophilia is characterized as an increase in immature or band neutrophils. This is usually seen in cases related to inflammation or infection. A degenerative left shift is considered more severe than a regenerative left shift. In a degenerative left shift, the immature neutrophils predominate. This means that the body is unable to meet the demand due to an overwhelming infection or inflammatory condition. Toxic changes may indicate incomplete maturation of a neutrophil due to intense stimulation or demand. Toxic changes may include a reduction in granulation, cytoplasmic vacuolation, and/or Dohle bodies which are seen in the cytoplasm. As a note, a regenerative left shift is where mature or segmented neutrophils still predominate
In general, it's uncommon for inflammation itself to exceed 40 x 10^9 L. When neutrophils exceed 70 x 10^9 L in dogs and 50 x 10^9 L in cats consider a neoplastic or paraneoplastic cause
Basophils
The role of a basophil is to initiate the immune and allergic reactions within body. Basophils are rarely seen in circulation. They also aren't normally found in the body tissues either like neutrophils or eosinophils. Mast cells are visually similar to basophils, but are found in the body tissues and do not enter into the bloodstream. Basophils are smaller than mast cells, have less cytoplasmic granules that are water soluble, and have a segmented nucleus. The granules of the basophil contain histamine and heparin. The histamine signals an acute allergic reaction and helps initiate inflammation. The heparin keeps the blood flowing to the site of an injured or damaged area. When levels of basophils are increased, it may indicate an allergic or hypersensitivity reaction in tissue
Eosinophils
The role of an eosinophil is to perform phagocytosis and to play a part in an allergic reaction or anaphylactic event by releasing anti-inflammatory substances from their granules. They're most effective against larger pathogenic organisms, such as protozoa or parasitic worms, but not as much against bacterial infections. You'll often see increased levels with allergic reactions and some parasitic infections. Blood is used for methods of transportation to their site of action
Monocytes
The role of a monocyte is to perform phagocytosis and process antigens within the body tissues or blood. In the bloodstream, they are able to engulf microorganisms and damaged blood cells. When higher levels of monocytes are found in the blood, it may indicate chronic inflammation, infection, or sepsis. When they enter their site of action into the body tissues from the bloodstream, they become known as tissue macrophages. They are most prevalent within the liver, spleen, lungs, and lymph nodes where they can contain or remove foreign invaders, old or damaged blood cells, and cellular debris. Due to their large size, they are able to ingest fungi, protozoa, viruses, and dead neutrophils. They're also known for their housekeeping role where they clean up leftover cellular debris after an inflammatory response or infection has occurred. Additionally, they're able to present antigens to lymphocytes to aide in the body's immune response
Lymphocytes
The role of a lymphocyte is to play a part in antibody production, humoral immunity, cytokine production, and cell-mediated immunity. B-cell lymphocytes perform the first two functions and T-cell lymphocytes perform the last two. They are predominately found within the lymphoid tissues where they have the ability to recirculate between those tissues and the bloodstream. T-cells play a role in cell-mediated immunity and activating B-cells. Out of the three lymphocytes, T-cells are found in the blood most often. T-cells may become cytotoxic or killer T-cells, helper T-cells, or suppressor T-cells. Killer T-cells actively eliminate any infected cells or sources of infection. Helper T-cells activate macrophages to eliminate unwanted microbes and release cytokines to increase the activity of B-cells, cytotoxic T-cells, and suppressor T-cells. B-cells produce antibodies against specific and designated antigens. Each B-cell is preprogrammed to recognize one antigen and produce that antibody for it. This is known as humoral immunity. Plasma cells are formed from B-cells after a response to an antigenic stimulus. Plasma cells aide in the production, storage, and release of antibodies known as immunoglobins. Both T and B-cells may become memory cells which wait in the lymphoid tissue for a second exposure to their specific antigen. The third lymphocyte is known as the natural killer cell. They destroy certain tumor cells and cells infected by viruses after direct contact. In circulation, lymphocytes are categorized as large or small. Large lymphocytes are described as young lymphocytes that eventually develop into small lymphocytes as they get older. Small lymphocytes have very little cytoplasm when compared to large lymphocytes
White blood cells function as a mechanism of defense for the body. There are five types of white blood cells; neutrophils, basophils, eosinophils, monocytes, and lymphocytes. Neutrophils, basophils, eosinophils, and monocytes perform phagocytosis as their defense mechanism while lymphocytes aide in the production of antibodies and cellular immunity. Neutrophils, basophils, and eosinophils have a multilobed and segmented nucleus. Eosinophils often have a two lobed nucleus and basophils have a two to three lobed nucleus. Lymphocytes have a single round shaped nucleus and monocytes have a nucleus without segments that may vary in it's shape. Neutrophils, basophils, and eosinophils all have cytoplasmic granules that may pick up stain while lymphocytes and monocytes do not. Neutrophil cytoplasmic granules are usually not visible. Basophil cytoplasmic granules stain blue and eosinophil's stain red
Neutrophils
The role of a neutrophil is to perform phagocytosis primarily in the body tissues. The cytoplasmic granules of the neutrophil contain lysosomal enzymes which help to kill any invading microorganisms that may cause disease or harm to the body. Neutrophils are transported by blood to their site of action. Right shift neutrophilia is characterized as an increase in mature or segmented neutrophils. This is usually seen in cases related to stress, fear, excitement, exercise, hyperadrenocorticism, or corticosteroid use. Hypersegmentation of neutrophils with greater than five nuclear lobes may be caused by prolonged corticosteroid use, vitamin B12 deficiency, and/or folate deficiencies. Left shift neutrophilia is characterized as an increase in immature or band neutrophils. This is usually seen in cases related to inflammation or infection. A degenerative left shift is considered more severe than a regenerative left shift. In a degenerative left shift, the immature neutrophils predominate. This means that the body is unable to meet the demand due to an overwhelming infection or inflammatory condition. Toxic changes may indicate incomplete maturation of a neutrophil due to intense stimulation or demand. Toxic changes may include a reduction in granulation, cytoplasmic vacuolation, and/or Dohle bodies which are seen in the cytoplasm. As a note, a regenerative left shift is where mature or segmented neutrophils still predominate
In general, it's uncommon for inflammation itself to exceed 40 x 10^9 L. When neutrophils exceed 70 x 10^9 L in dogs and 50 x 10^9 L in cats consider a neoplastic or paraneoplastic cause
Basophils
The role of a basophil is to initiate the immune and allergic reactions within body. Basophils are rarely seen in circulation. They also aren't normally found in the body tissues either like neutrophils or eosinophils. Mast cells are visually similar to basophils, but are found in the body tissues and do not enter into the bloodstream. Basophils are smaller than mast cells, have less cytoplasmic granules that are water soluble, and have a segmented nucleus. The granules of the basophil contain histamine and heparin. The histamine signals an acute allergic reaction and helps initiate inflammation. The heparin keeps the blood flowing to the site of an injured or damaged area. When levels of basophils are increased, it may indicate an allergic or hypersensitivity reaction in tissue
Eosinophils
The role of an eosinophil is to perform phagocytosis and to play a part in an allergic reaction or anaphylactic event by releasing anti-inflammatory substances from their granules. They're most effective against larger pathogenic organisms, such as protozoa or parasitic worms, but not as much against bacterial infections. You'll often see increased levels with allergic reactions and some parasitic infections. Blood is used for methods of transportation to their site of action
Monocytes
The role of a monocyte is to perform phagocytosis and process antigens within the body tissues or blood. In the bloodstream, they are able to engulf microorganisms and damaged blood cells. When higher levels of monocytes are found in the blood, it may indicate chronic inflammation, infection, or sepsis. When they enter their site of action into the body tissues from the bloodstream, they become known as tissue macrophages. They are most prevalent within the liver, spleen, lungs, and lymph nodes where they can contain or remove foreign invaders, old or damaged blood cells, and cellular debris. Due to their large size, they are able to ingest fungi, protozoa, viruses, and dead neutrophils. They're also known for their housekeeping role where they clean up leftover cellular debris after an inflammatory response or infection has occurred. Additionally, they're able to present antigens to lymphocytes to aide in the body's immune response
Lymphocytes
The role of a lymphocyte is to play a part in antibody production, humoral immunity, cytokine production, and cell-mediated immunity. B-cell lymphocytes perform the first two functions and T-cell lymphocytes perform the last two. They are predominately found within the lymphoid tissues where they have the ability to recirculate between those tissues and the bloodstream. T-cells play a role in cell-mediated immunity and activating B-cells. Out of the three lymphocytes, T-cells are found in the blood most often. T-cells may become cytotoxic or killer T-cells, helper T-cells, or suppressor T-cells. Killer T-cells actively eliminate any infected cells or sources of infection. Helper T-cells activate macrophages to eliminate unwanted microbes and release cytokines to increase the activity of B-cells, cytotoxic T-cells, and suppressor T-cells. B-cells produce antibodies against specific and designated antigens. Each B-cell is preprogrammed to recognize one antigen and produce that antibody for it. This is known as humoral immunity. Plasma cells are formed from B-cells after a response to an antigenic stimulus. Plasma cells aide in the production, storage, and release of antibodies known as immunoglobins. Both T and B-cells may become memory cells which wait in the lymphoid tissue for a second exposure to their specific antigen. The third lymphocyte is known as the natural killer cell. They destroy certain tumor cells and cells infected by viruses after direct contact. In circulation, lymphocytes are categorized as large or small. Large lymphocytes are described as young lymphocytes that eventually develop into small lymphocytes as they get older. Small lymphocytes have very little cytoplasm when compared to large lymphocytes
Sources:
Colville, Thomas, and Joanna M. Bassert. Clinical Anatomy and Physiology for Veterinary Technicians. 2nd ed. Mosby Elsevier, 2008.
Poli, Gerardo. MiniVet Guide: Companion Animal Medicine. InHouse Publishing, 2016.
Colville, Thomas, and Joanna M. Bassert. Clinical Anatomy and Physiology for Veterinary Technicians. 2nd ed. Mosby Elsevier, 2008.
Poli, Gerardo. MiniVet Guide: Companion Animal Medicine. InHouse Publishing, 2016.