Alpha‐Naphthyl Acetate Esterase Activity in Human Lymphocytes: Distribution in Lymphocyte Subpopulations and in Mitogen‐activated Cells

Abstract

The cytochemical demonstration of nonspecific .alpha.-naphthyl acetate esterase (ANAE) activity in human peripheral blood mononuclear cells was studied. Different staining patterns were found, allowing differentiation of mononuclear cells into macrophages (strong granular cytoplasmic activity), B [bone marrow-derived] lymphocytes (negative reaction), T.gamma. lymphocytes (thymus-derived cells bearing Ig[immunoglobulin]G Fc receptors) (granular scattered reaction) and T non-.gamma. (devoid of IgG Fc receptors) lymphocytes (single cytoplasmic ANAE spot). During the early phases of phytohemagglutinin (PHA)- and concanavalin (Con) A-induced activation, the reactivity of most lymphocytes became granular and scattered, similar to that found in T.gamma. cells. Blast cells generating in successive phases appeared devoid of detectable enzymatic activity. T cells showing granular, scattered reactivity may represent a population of activated cells. The redistribution of enzymatic activity could represent a preliminary step leading to secretion (lymphokine-like?) of enzyme from cytoplasm in the course of cell activation.