Dissociation of Interleukin-2-mediated Cell Proliferation and Interleukin-2 Receptor Upregulation in Adult T-cell Leukemia Cells

We studied cell proliferation and interleukin-2 (IL-2) receptor upregulation mediated by exogenous IL-2 in leukemic cells from adult T-cell leukemia (ATL) patients to characterize some aspects of abnormal IL-2 receptor expression in ATL. Leukemic cells from 7 ATL patients examined showed no or very poor proliferative response to IL-2 though they expressed IL-2 receptors without any stimulation. In contrast, ATL leukemic cells cultured with IL-2 for 2 days expressed about twice as many IL-2 receptors as those of cells cultured without IL-2. Thus, in ATL leukemic cells, there seems to be a dissociation between the signal(s) for two different effects mediated by IL-2, cell proliferation and IL-2 receptor upregulation.