White blood cells are important components of the body’s immune system. These cells are also known as leukocytes. There are different types of white blood cells which are broadly divided into the granulocytes and agranulocytes named so due to the presence of granules within the cell.
Types of White Blood Cells
There are three types of granulocytes – neutrophils, eosinophils and basophils. The neutrophils are important cells that fight off invading pathogens (bacteria, fungi, bacteria). The eosinophils also play a role in infection usually secondary to parasitic infection as well as in allergic reactions. The basophils are mainly mediators of allergic reactions (hypersensitivity) to specific allergens.
The agranulocytes include lymphocytes and monocytes. There are several types of lymphocytes including B-cells, T-cells and natural killer cells. The B-cells and T-cells fight off invading pathogens while the natural killer cells target cancerous or infected body cells. Monocytes are highly versatile immune cells that help with fighting off infection by coordinating immune activity and differentiating into other immune cells that “mop” up the site of infection.
Terms for Excess White Blood Cells
When there is an excess of a specific type of white blood cell in the bloodstream, the suffix -osis or -ia is appended to the end of the cell name if it ends with an ‘e’ or ‘l’ respectively.
- Leukocytosis is a higher than normal quantity of circulating white blood cells.
- Neutrophilia is a higher than normal number of circulating neutrophils. It is also known as neutrophil leukocytosis.
- Eosinophilia is higher than normal number of circulating eosinophils.
- Basophilia is a higher than normal number of circulating basophils.
- Lymphocytosis is a higher than normal number of circulating lymphocytes.
- Monocytosis is a higher than normal number of circulating monocytes.
- Strenuous exercise
- Bacterial or fungal infection
- Trauma particularly surgery and burns.
- Chronic inflammation not due to an infection and especially in autoimmune diseases like rheumatoid arthritis, ulcerative colitis and Crohn’s disease.
- Tissue death (infarction) by loss of oxygenated blood in conditions like myocardial infarct (heart attack) and pulmonary embolus (blood clot in the lung).
- Cancer including lymphomas.
- Myeloproliferative diseases which are excessive and abnormal growth of certain blood cells in the bone marrow and includes polycythaemia and chronic myelogenous leukaemia.
- Parasitic infection and infestation
- Allergies (atopy) particularly the allergic triad of asthma, eczema and allergic rhinitis
- Drug hypersensitivity
- Cancers including lymphomas.
- Myeloproliferative diseases (bone marrow) like acute myelogenous leukemia.
- Connective tissue diseases where the structural framework of the body or specific organs is targeted often by the immune system and often involves the blood vessels like polyarteritis nodosa.
- Severe acute inflammation (non-infectious) like with acute exacerbation of allergic conditions.
- Acute exacerbation of chronic inflammatory conditions like inflammatory bowel disease.
- Iron deficiency
- Polycythemia (excess red blood cells / hemoglobin)
- Myeloproliferative disease like chronic myeloid leukaemia
- Some viral infections like smallpox, chicken pox and influenza
- Infection, particularly acute and subacute infections – viral and bacterial.
- Lymphoproliferative diseases where there is an excess of lymphocytes often related to immune dysfunction. Some of these diseases include cancers like chronic lymphocytic leukemia and lymphomas.
- After surgical removal of spleen.
- Endocrine diseases like an underactive adrenal gland or ovaractive thyroid gland.
- Infection particularly subacute and chronic bacterial infections.
- Parasitic diseases
- Autoimmune diseases
- Connective tissue diseases
- Cancers, mainly solid tumors, but may also be seen with myelogenous leukemias and lymphomas.