The phenotype of human eosinophils, basophils, and mast cells

Abstract

Basophils, eosinophils, and mast cells (MCs) are specialized effector cells of the immune system. They are involved in inflammatory and allergic reactions and store and release multifunctional mediator molecules including vasoactive substances, lipid mediators, or cytokinesJ -3 Several different agonists, such as immunoglobulin, complement components, peptides, or cytokines and their specific receptors are involved in the activation of basophils, eosinophils, and MCs for mediator secretion? -~ MCs, basophils, and eosinophils originate from uncommitted multipotent progenitor cells. 5 Precursor cells giving rise to eosinophils and basophils (CFU eo/ba) are responsive to T cell-derived factors,6, 7 whereas MC precursor cells (CFUMAST) are responsive to stroma-cell-derived cytokines. 8 Basophils, eosinophils, and MCs form separate cell lineages and the committed precursor cells (giving rise to either MCs, basophils, or eosinophils) clearly are different cells?' 9 Basophils and eosinophils usually complete their differentiation in the bone marrow. After maturation both cells leave the marrow and are circulating cells. Under certain circumstances, and in particular on cell activation, basophils and eosinophils may leave the bloodstream to enter extravascular (inflamed) tissues. 3 In contrast, MCs derive from circulating multipotent progenitor cells (CFU-MIX), and after extravasation/homing of progenitors, undergo and complete their differentiation in extramedullary organs. 1° However, MCs may also migrate in the tissues and appear at sites of inflammation.