Mast cells and basophils in acquired immunity.

In this review we describe the basic biology of mast cells and basophils and discuss their proposed effector and immunoregulatory roles in acquired immunity, particularly the IgE-associated immune responses. While mast cells and basophils share a number of similarities, they also differ in many aspects of natural history and function. Both mast cells and basophils express the high affinity receptor for immunoglobulin E (Fc epsilon RI) on their surface and can be activated to secrete diverse preformed, lipid and cytokine mediators after crosslinking of Fc epsilon RI-bound IgE with bi- or multivalent antigen. Thus, both cell types can represent important effector cells, as well as potential immunoregulatory cells, in IgE-mediated acquired immunity. However, mature mast cells are long-term residents of vascularized tissues, whereas basophils are granulocytic leukocytes that circulate in mature form and must be recruited into tissues that are sites of inflammatory or immune responses. The similarities and differences in the natural history, mediator content and other features of mast cells and basophils not only strongly indicate that these cells represent distinct hematopoietic lineages that can express complementary or overlapping functions, but also offer insights into the specific roles of these cells in acute, 'late phase' and chronic aspects of adaptive or pathological IgE-associated acquired immune responses.