Monday, 9 June 2014

Basophils

Basophils are quite few and far between, making up only around 0.01-0.3% of all circulating leukocytes; nevertheless, they pack quite a punch. Now, as I say, basophils are circulating white blood cells, they do not have a home like mast cells - their fellow granulocytes - do. Instead, like neutrophils and immature dendritic cells, they circulate in the blood stream awaiting an invasion by a pathogen. When pathogens are detected by immunocompetent cells, basophils can be recruited from the bloodstream as part of the inflammatory response.

As granulocytes, the primary function of basophils is to degranulate when stimulated to do so. As with mast cells, these granules contain histamine and heparin, as well as cytokines and a number of other things. One of the most notable things released by basophils is interleukin 4 (IL-4), a very important cytokine.

Basophils exhibit a number of receptors, including our friend FcεRI. As with mast cells, basophils bind with IgE antibodies, which are involved in the degranulation process. Again, it is important to appreciate that basophil degranulation will be triggered by specific pathogens - i.e. the ones which bind to IgE antibodies. In this way the right response to a given pathogen is produced.

(a) An image of a basophil granulocyte. (Image courtesy Department of Histology, Jagiellonian University Medical College (via Wikipedia))
(b) A schematic representation of a basophil. (Image courtesy "A. Rad" (via Wikipedia))

Figure 1.55: The basophil

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