Mast Cells Basophils and Eosinophils

Mast cells, basophils, eosinophils, monocytes, and neutrophils all originate from a CD34+CD117+ cell. Although mast cells were reported to arise separately from a CD34+CD117+CD13+ precursor subset,220 a recently identified antibody, 97A6, labels distinct CD34+CD117+ bone marrow progenitors that give rise to both mast cells and basophils. Cultured CD34+97A6+ precursors also yield eosinophil and multilineage (basophil-eosinophil-macrophage-neutrophil) colonies; however, only mast cells and basophils react with the 97A6 antibody among all hematopoietic or nonhematopoietic cell types.221 Both cell types share metachromatic staining properties and express high-affinity surface receptors for the Fc portion of IgE (FceRI), but differ in tissue distribution, granular contents, morphology, immunophenotype, and production, as well as dependence on growth factors.222-227 Mast cells are found throughout connective tissues and mucosal surfaces of various organs, where they demonstrate tissue-specific biological features and characteristic antigen profiles, whereas basophils are circulating granulo-cytes. Both cell types express the panleukocyte antigens CD45, CD33, CD68 (in cytoplasmic granules), and CD9, a molecule of platelets, B cells, and monocytes. Both cell types lack HLA-DR, lymphoid antigens, and CD34. Mast cells express CD14, react with antibodies typical for late-stage macrophage differentiation, and express ICAM-1 (CD54).

Mast cells express c-kit (CD117), and their growth and development require stem cell factor. In contrast, CD117 is lost from basophils during cell maturation. Basophils, on the other hand, express CD123 (interleukin[IL]-3Ra), and IL-3 is their major growth and differentiation factor. Furthermore, basophils differ from mast cells and eosinophils by their expression of Bsp-1, CD26 (dipeptidylpeptidase IV), and CDw17 (lac-tosylceramide). Basophils express CD11b/CD18, and the nerve growth factor receptor homologue CD40, CD15s and the T-cell activation antigens CD38 and CD25.

Eosinophils express both CD25 and CD122 (forming a high-affinity IL-2 receptor), are weakly CD4+ and similar to monocytes,228 and express several adhesive structures, including HLA-DR; the p2 integrins CD11a and CD11b; two CD49/CD29 P1 integrins (VLA-4 and VLA-6); CD44; three members of the Ig gene superfamily, namely CD50 (ICAM-3), CD58 (LFA-3), and CD31 (PECAM-1); and CD43, in addition to complement regulatory proteins [CD35 (CR1, C3b receptor), CD46 (membrane cofactor protein, MCP), CD55 (decay-accelerating factor, DAF), and CD59 (MAC inhibitor)], and the myeloid antigens CD13,

CD65, and CD15.63 In their secondary granules eosinophils contain multiple cytokines, such as granulocyte macrophage-colony-stimulating factor, IL-2, IL-6, IL-5, tumor necrosis factor (TNF)-a, nerve growth factor, and stem cell factor.229

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