Alpha-naphthyl acetate esterase activity in human lymphocytes: distribution in lymphocyte subpopulations and in mitogen-activated cells.

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 lymphocytes (negative reaction), Tgamma lymphocytes, i.e. bearing IgG Fc receptors (granular scattered reaction), and T non-gamma lymphocytes, i.e. devoid of IgG Fc receptors (single cytoplasmic ANAE spot). During the early phases of phytohaemagglutinin (PHA)- and concanavalin A (Con A)-induced activation, the reactivity of most lymphocytes became granular and scattered, similar to that found in Tgamma cells. Blast cells generating in successive phases appeared devoid of detectable enzymatic activity. The hypothesis is put forth that T cells showing granular, scattered reactivity represent a population of activated cells and that 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.