Basophil leukocytes, receptors

Basophils and Eosinophils. These two types of granulocyte represent only a small proportion of the circulating leukocytes. The basophil possesses receptors specific for the Fc portion of IgE molecules. It is involved in allergic reactions and can play a role in the clinical state of anaphylaxis, which is a life-threatening allergic response. Eosinophils are involved with the immune reactivity of drug allergies and with the body s immune response to parasitic infestations such as worms (see chapter 9). 

Eorssmann, U., Uguccioni, M., Loetscher, P., Dahinden, C. A., Langen, H., Thelen, M., and Baggiolini, M. (1997). Eotaxin-2, a novel CC chemokine that is selective for the chemokine receptor CCR3, and acts like eotaxin on human eosinophil and basophil leukocytes. J. Exp. Med. 185, 2171-2176. 

Specific receptors on tissue mast cells or circulating basophil leukocytes bind the Fc portion of the IgE molecule and the antibody becomes cell-fixed. The Fc receptors for IgE have been isolated and purified from a rat basophil leukemia (Z> ) There are about 2 to 8 x 105 of these receptors on a mast cell (9) and it appears that the receptor protein is deeply embedded in the membrane with little exposure to the external milieu The... 

Figure 1. Sequence of events in the secretion of mediators from mast cells or basophil leukocytes. IgE antibody (Y) binds to the cell membrane at specific receptor sites to sensitize the ceU. Antigen cross-linking IgE molecules provide a membrane signal to the cell which sets in motion a chain of biochemical events. The membrane surrounding the granules (%), which contains the mediators, fuses with the cell membrane (exocytosis) to allow the mediators to escape into the surrounding medium. The granule matrix behaves as an ion-exchange resin releasing histamine and taking up Na...

Neutrophils, monocytes, macrophages, eosinophils, basophils, and polymorphonuclear leukocytes are all affected by several or all of these factors. Binding to specific receptors results in a variety of changes in the cells. These include alterations in membrane potential, cyclic nucleotide levels, and ion fluxes (Na+, K+, Ca2+) as well as increased methylation of specific proteins. 

The identification of basophil cells was initially based on the presence of the high affinity receptor for immunoglobulin E and expression of CD45 or protein tyrosine phosphatase receptor type C (PTPRC) also known as leukocyte common antigen, a FTP signaling molecule found on all leukocytes. To distinguish basophils from other leukocyte populations, a number of selection strategies are possible. One procedure... 

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