Ultrastructural Morphology of Basophils and Mast Cells

Abstract

Although basophils and mast cells are closely related cells, as defined by morphological, functional, and biochemical criteria, they are sufficiently different to be assigned to one of these two lineages in most species (A. M. Dvorak, 1986b, 1988b; A. M. Dvorak et al., 1983a). The general and specific ultrastructural criteria for doing so are listed in Table I. Since immature basophils, or basophilic myelocytes, are large mononuclear cells filled with metachromatic, immature granules (A. M. Dvorak, 1988a; A. M. Dvorak and Monahan, 1985a; A. M. Dvorak et al., 1982c, 1985c), they can be confused with mature, large, metachromatic granule-filled mononuclear mast cells. The ultrastructural criteria for distinguishing nonmalignant basophilic myelocytes from mast cells are listed in Table II. If the general rules for maturation of granulocytes are applied to each identification problem, it should be possible to distinguish immature, nonmalignant basophilic myelocytes from mature, nonmalignant mast cells.