Early calcium signaling and calcium requirements for the IL-2 receptor expression and IL-2 production in stimulated lymphocytes.

Two kinds of lymphocyte populations were prepared from human resected tonsils: one was a mixed population consisting of T cells, B cells, other lymphocytes, and a few macrophages, and the other was a T-enriched population obtained by removing adherent cells from the mixed population with a nylon wool column. A transient rise in cytosolic free calcium ion concentration ([Ca2+]i) was observed in both the populations within a few minutes of stimulation with concanavalin A (Con A). However, emergence of cells which had high [Ca2+]i after 4 min of Con A stimulation was observed practically only in the mixed population. The [Ca2+]i elevation occurring within a few minutes of stimulation in both populations was interpreted as being due to a release from the intracellular Ca-storing organelles, whereas the high [Ca2+]i in a group of cells after 4 min of Con A stimulation in the mixed population was caused by an influx of extracellular calcium that probably corresponds to a transient enhancement of Ca2+ uptake observed only in the mixed population during early stimulation. Con A induced both interleukin 2 receptor (IL-2R) expression and interleukin 2 (IL-2) production. A nonmitogenic lectin, wheat germ agglutinin (WGA), also induced a rise in the [Ca2+]i within a few minutes. WGA induced IL-2 production, but did not induce IL-2R expression. Chelation of extracellular calcium with EGTA at the time of Con A addition resulted in a decrease in IL-2R expression, IL-2 production, and DNA synthesis, but not when CaCl2 equimolar to EGTA was present in the culture medium. Chelation of calcium 12 hr after Con A stimulation decreased IL-2R expression, but had no effect on IL-2 production. These results indicate that IL-2 production required Ca2+ only in the early (G0) stage and that IL-2R expression was dependent on Ca2+ in both the G0 and the G1 stages.