Interleukin 2 mediates the inhibition of oligodendrocyte progenitor cell proliferation in vitro

In the immune system, T-lymphocyte proliferation depends on interleukin 2 [IL-2 (T-cell growth factor)] interaction with specific receptors. In this study we show that IL-2 can specifically inhibit the proliferation of neonatal rat oligodendrocyte progenitor cells cultured in a serumless, chemically defined medium (oligodendrocyte-defined medium; ODM). IL-2 inhibited both [3H]thymidine incorporation and increase in cell number. Specificity was shown by precipitating IL-2 activity with anti-IL-2 antiserum. Furthermore, growth inhibition depended on the expression of Tac (an anti-IL-2 receptor monoclonal antibody)-positive receptors (IL-2 receptor). When cells were cultured in the presence of IL-2, both Tac-positive staining and growth inhibition were no longer expressed. The addition of interleukin 1 had no effect on [3H]thymidine incorporation or changes in cell number. However, when IL-1 was subsequently added together with IL-2, Tac expression and IL-2-mediated inhibition of cell proliferation was induced. This inhibitory effect was not due to a sensitive subpopulation because greater than 90% of the culture was Tac positive. Taken together, these data show that IL-2 can specifically inhibit oligodendrocyte proliferation and acts via Tac-positive receptors.