Mechanisms of Interleukin-2-Mediated Signaling and role of Calcium in T cell Mitogenesis

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.

Calcium ion influx during mitogenic stimulation of lymphocytes.

“…We used Con A as a stimulator instead of PHA when measuring the [Ca2+]i in single cells because PHA caused more cell aggregation than Con A did in the initial phase of mitogenesis. Moreover, Con A is more suitable for the analysis of mitogenesis mediated by IL-2, since Con A can be easily removed from the lymphocyte cell membrane by washing with a-methyl mannoside (12), allowing us to determine the individual effects of the mitogen, Con A, and of IL-2 on Ca2+ transport. 45CaCl2 uptake in lymphocytes treated with Con A was quite similar to that with PHA (data not shown).…”

“…It in part comes from conversion of intracellular Ca2+ from a bound to an unbound state. The enhancement of 45CaC12 uptake caused by Con A was not observed in T cells prepared using a nylon wool column (12), but a transient increase in the [Ca2+]i was observed using fura-2 (Nakabayashi, H. et al in preparation). The subsets of cells which were induced to take up Ca2+ due to the addition of Con A might have adhered to the nylon wool.…”

Measurement of the cytosolic free calcium ion concentration of individual lymphocytes by microfluorometry using quin 2 or fura-2.

“…We reported the enhancement of Ca2+ uptake and the rise in the [Ca2+]i in the initial step of stimulation, but these events occurred transiently (7). The role of the augmentation of Ca2+ uptake and of the [Ca2+]i, and the necessity of Ca2+ have been discussed by many researchers (2,3,6,7,10,16).…”

Differential response of cells of mixed population and of T-enriched population to concanavalin A, and reconstitution of lymphocyte response by phorbol myristate acetate or interleukin 2.

“…About 33% of the cells were helper T cells, about 8 killer/cytotoxic T cells and about 49% B cells as determined with monoclonal antibodies (MAbs) T4, T8 and B1 (Coulter Immunology), respectively, and about 40% of the cells formed rosettes with sheep red blood cells (SRBC). To enrich for T lymphocytes, the adherent cells and B cells were depleted by passage of the cells of mixed population through a nylon wool column (Komada et al 1985). We referred to them as the cells of T-enriched population.…”