White blood cells: Types of WBCs, their role in fighting pathogens and what fluctuations in their numbers could mean

White blood cells (WBCs) make up about one percent of all the cells in our blood. These cells make up our immune system and are responsible for fighting infections and pathogenic microbes that enter our body.

Myupchar December 03, 2020 21:25:18 IST
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White blood cells: Types of WBCs, their role in fighting pathogens and what fluctuations in their numbers could mean

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Given the COVID-19 pandemic, most of us have been hyper-focused on our health and, in particular, the immune system. The general public knows more about how the human body fights off infections and micro-organisms than ever before. One area of interest when it comes to understanding immunity is the role played by white blood cells.

White blood cells (WBCs) make up about one percent of all the cells in our blood. These cells make up our immune system and are responsible for fighting infections and pathogenic microbes that enter our body.

Normally, the human body has about 4,000 to 11,000 WBCs per mm3 of blood — about 4.5 to 11 X 109 per litre. These cells consist of granulocytes — neutrophils, basophils and eosinophils - and agranulocytes — lymphocytes (B and T cells) and monocytes.

Any fluctuation (both higher and lower than normal) in the number of WBCs in the body indicates a disease or infection.

Here is all you need to know about the various types of white blood cells and your WBC count.

Types of white blood cells

The following are the types of WBCs and their common functions:

Granulocytes: Granulocytes are named after the peculiar granules noticed in their cytoplasm when seen under the microscope. These cells include:

  • Neutrophils: Neutrophils are the first types of WBCs to reach an infection site. They eliminate the pathogen by either killing or eating it.
  • Eosinophils: Eosinophils are mainly responsible for fighting parasites. Their numbers increase in case of allergic reactions and parasitic infections.
  • Basophils: Basophils are the rarest type of WBCs and are involved in the inflammation process.

Agranulocytes: These WBCs do not have any granules present in them and are of the following types:

  • Lymphocytes: Lymphocytes include B and T cells, which are involved in the acquired immunity (the one you generate after being exposed to an antigen) of the body.
  • Monocytes: Monocytes enter tissues and turn into macrophages, which then eat away antigens and also interact with lymphocytes to eliminate the pathogen.

WBC count

A WBC count lower than 3,500 per mm3 of blood is called leukopenia. It may occur due to conditions like:

  • Severe bacterial infections
  • Viral infections
  • Autoimmune disorders
  • Side effects of medications and radiotherapy
  • Cancers that affect the bone marrow

A WBC count higher than 11,000 per mm3 of blood is called leukocytosis. It may occur due to:

  • Pregnancy
  • Asthma
  • Allergies
  • Inflammatory conditions
  • Leukaemia
  • Stress

Total leucocyte count is used to determine the WBC count in the body while a differential leucocyte count test gives the number of each individual type of WBC.

What changes in individual WBC levels indicate

Neutrophils: Higher than normal levels of neutrophils suggests a trauma, acute infection or conditions like rheumatoid arthritis, gout and thyroiditis. Lower than normal neutrophil levels are indicative of viral infection, chemotherapy or severe bacterial infection.

Eosinophils: Higher than normal eosinophil levels indicate allergies, cancer and parasitic infections. Lower than normal levels could be a result of excessive alcohol intake or increased production of cortisol.

Basophils: Increased basophil levels are indicative of conditions like chickenpox, allergies, chronic myelogenous leukaemia and reduced basophil levels could be due to cancer, severe injury and acute infection.

Monocytes: Higher than normal levels of monocytes are indicative of tuberculosis, leukaemia, chronic inflammatory disease and parasitic infections. Lower levels could occur if you’re taking certain drugs or in case of certain infections and some cancers.

Lymphocytes: The number of lymphocytes increases in conditions like viral or bacterial infections or any inflammatory condition while their number reduces during conditions like HIV/AIDS, sepsis, chemotherapy and due to steroid usage.

For more information, read our article on Immune system and immunity

Health articles in Firstpost are written by myUpchar.com, India’s first and biggest resource for verified medical information. At myUpchar, researchers and journalists work with doctors to bring you information on all things health.

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