Cytochemical demonstration of increased adenosine triphosphatase activity in lymphocytes activated in vitro by phytohaemagglutinin or by the mixed lymphocyte reaction.

Cytochemical investigations of ATPase activity were performed on lymphocytes isolated from peripheral blood and activated in vitro by phytohaemagglutinin or by the two-way mixed lymphocyte reaction. Uncultured lymphocytes showed very little activity localized in small granules. The activity increased markedly during transformation. In fully transformed and actively proliferating cells, the ATPase activity was intense and localized in a crescentic perinuclear area of cytoplasm which was pale-staining and vesicular in Giemsa-stained preparations. In mitotic cells, the activity was in discrete granules or elongated structures suggestive of mitochondria, scattered throughout the cytoplasm. The ATPase activity had a pH optimum of 8.5 to 9.5 and was strongly inhibited at pH 7.5. The activity was stimulated by Ca2+ and Mg2+ and was inhibited by p-chloromercuribenzoate but not by oligomycin, which appeared to enhance the reaction. Lead nitrate at a concentration of 3 mM did not inhibit the reaction.