In addition to defending the body from bacteria, viruses and parasites, white blood cells also play a part in the inflammatory response. White blood cells have many vital yet subtle roles in promoting and regulating inflammation. Examining the functions of such cells can help us better understand the complex relationships between immunity and inflammation as well as allergies and autoimmune diseases.
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Neutrophils are the most abundant type of white blood cell in circulation and represent the body’s first line of defense against invading bacteria. Neutrophils can release substances that kill bacteria and can also eat bacteria through the process of phagocytosis. Dr. Ken Miyasaki from UCLA explains that neutrophils also release a number of substances involved in the inflammatory response. After injury, neutrophils are recruited to sites of inflammation where they prevent infection and also help to recruit other inflammatory cells to sites of inflammation.
Eosinophils help defend the body against parasites. Eosinophils also mediate a number of allergen responses that might link allergies and inflammation. A 2009 article in the Proceedings of the American Thoracic Society by John Fahy explains how eosinophils can contribute to airway inflammation during asthma. As eosinophils accumulate in the lungs of individuals with asthma, neutrophils can join up with eosinophils to exacerbate airway restriction and inflammation.
Basophils are white blood cells that play an important role in the inflammatory process. The National Institutes of Health website MedlinePlus explains that basophils release histamine and heparin after they are recruited to sites of injury and inflammation. Histamine acts to relax blood vessels and increase blood flow to inflamed tissues. Heparin is an anticoagulant that allows blood to easily flow to areas of damaged tissues.
Mast cells are an important mediator of inflammatory responses. Mast cells are similar to basophils in that they secrete heparin and histamine to promote blood flow to damaged and inflamed tissues. Mast cells and basophils, however, have slightly different cellular origins. Additionally, basophils circulate in a mature form whereas circulating mast cells do not mature until they encounter a site or injury or inflammation. The textbook Immunobiology by Charles Janeway summarizes the role of mast cells in allergy, inflammation, asthema and autoimmune diseases.