White blood cells are also called leukocytes. They protect the body against infections and external threats such as disease-causing bacteria and viruses. Some leukocytes destroy body's internal threats which could be mutated DNA that can multiply becoming cancerous.
Leukocytes are majorly divided into two groups, based on cytoplasmic granular content: Granular leukocytes containing abundant granules like eosinophils, lisinoprils and basophils, and agranular leukocytes with less visible granules such as monocytes and lymphocytes (OpenStax College, 2013).
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Neutrophils respond rapidly to the site of infection and are phagocytes with a preference for bacteria. Their granules contain an enzyme known as lysozyme that is capable of lysing bacterial cell wall, oxidants that oxidize essential components of the bacteria and proteins that bind to the bacterial and fungal plasma membranes, puncturing them hence causing cellular contents leakage. Eosinophil granules contain antihistaminic molecules which counter effects of inflammatory chemicals produced by basophils and mast cells. Some granules are also toxic to parasitic worms. They are also phagocytic. The main function of basophils is to intensify inflammatory responses (Zabriskie, 2009).
Lymphocytes are divided into three major groups including natural killer cells, B cells and T cells. Natural killer cells provide non-specific immunity. They function in recognizing cancerous cells, cells infected with viruses and cells containing abnormal surface proteins. B cells and T cells are involved in specific immunity. T cells attack foreign or diseased cells. B cells produce specific antibodies that have an affinity to foreign components (antigens) in the body. Exposure to pathogens leads to the formation of memory cells that last for years from a variety of T and B cells, which rapidly responds to any subsequent attacks. Monocytes leave the circulation to become macrophages which phagocytose debris, foreign pathogens, worn out erythrocytes and damaged cells. They produce antimicrobial defensins and chemotactic chemicals which attracts other leukocytes to the site of infection (OpenStax College, 2013).
References
OpenStax College. (2013). Anatomy & Physiology . New York: Cambridge University Press.
Zabriskie, J. B. (Ed.). (2009). Essential Clinical immunology . New York: Cambridge University Press.
