Inhibition of mitogen-induced lymphocyte proliferation by ouabain: interference with interleukin 2 production and interleukin 2 action.

Since the discovery of IL 2 it has been possible to dissect the mitogenic activation of T lymphocytes into two steps: first, the production of IL 2; and second, the response of IL 2-dependent T cell blasts to IL 2. We investigated the influence of ouabain, a known inhibitor of T cell activation, on the production of and the response to IL 2 in mouse T lymphocytes. Ouabain dose-dependently inhibited DNA synthesis in Con A activated C57BL/6 spleen cells; inhibition below background levels occurred at a concentration of 5 X 10(-4) mol/liter. The action of IL 2 was assayed on a mouse T cell line, named M 2, derived from C57BL/6 spleen cells and maintained in continuous IL 2-dependent culture for more than 21 mo. Ouabain dose-dependently inhibited the response of these cells to mouse IL 2 with optimal inhibition at 10(-3) mol/liter ouabain. The production of IL 2 by Con A-stimulated C57BL/6 spleen cells was also totally inhibited by 10(-3) mol/liter ouabain; 10(-4) mol/liter ouabain inhibited IL 2 production partially, and 10(-5) mol/liter and 10(-6) mol/liter ouabain had no inhibitory effect. The ouabain-mediated inhibition of IL 2 production and of IL 2 action was not due to a nonspecific toxicity, because the preincubation of spleen cells with 10(-3) mol/liter ouabain for 24 hr did not impair their ability to produce IL 2, nor was the response of M 2 cells to exogenously added IL 2 abrogated by the preincubation of the cells with 10(-3) mol/liter ouabain. The data suggest that ouabain acts on two steps during the induction of T cell activation.