Variable expression of activation-linked surface antigens on human mast cells in health and disease

Mast cells (MC) are multipotent effector cells of the immune system. They c ontain an array of biologically active mediator substances in their granule s. MC also express a number of functionally important cell surface antigens , including stem cell factor receptor (SCFR=kit=CD117), high affinity IgER (Fc epsilon RI), or C5aR (CD88). Respective ligands can induce or promote d egranulation, migration, or cytokine production. Other integral surface mol ecules can mediate adhesion or cell aggregation. Recent data suggest that a number of critical molecules are variably expressed on the surface of huma n MC. In fact, depending on the environment (organ), stage of cell maturati on, type of disease, and other factors, MC express variable amounts of acti vation-linked antigens (CD25, CD63, CD69, CD88), cell recognition molecules (CD2, CD11, CD18, CD50, CD54), or cytokine receptors. At present, however, little is known about the mechanisms and regulation of expression of such antigens. The present article gives an overview of MC phenotypes in health and disease, and attempts to provide explanations for the phenotypic variab ility of MC.