No abstract

Calmodulin was purified from human tonsillar lymphocytes utilizing calcium-dependent binding of calmodulin to fluphenazine-Sepharose. The molecular weight and phosphodiesterase activation of the lymphocyte calmodulin were very similar to those of purified bovine brain calmodulin. Trifluoperazine (TFP), a calmodulin inhibitor, suppressed lymphocyte stimulation as assessed by 3H-thymidine incorporation into DNA of lectin-stimulated lymphocytes. TFP had no effect on the early 45Ca2+ uptake induced by mitogenic lectins, although this latter was inhibited by verapamil which also suppressed the 3H-thymidine incorporation. The results are in keeping with the interpretation that the inhibition of T cell stimulation by TFP was not due to suppression of Ca2+ uptake, but due to inactivation of Ca(2+)-calmodulin complex which might be formed subsequent to Ca2+ entry into the cell.

No abstract

In T lymphocytes stimulated by concanavalin A (Con A), interleukin 2 (IL-2) acts on the late G1 stage of the cell cycle. Ca2+ uptake by T cells was not enhanced with the stimulation of Con A (initiation) or IL-2 (late G1 stage), but Ca2+ requirement was observed at the two stages. These results indicate that the enhancement of Ca2+ uptake is not necessary, but intracellular Ca2+ may act as an important messenger in T cell mitogenesis.

ABSTRACT. The uptake of free calcium ion (Ca2+) in PHA-or A23187-stimulated lymphocytes was measured using 45CaCl2 and 3H-water.