IDENTIFICATION AND PURIFICATION OF HUMAN STAT PROTEINS ACTIVATED IN RESPONSE TO INTERLEUKIN-2

A key cytokine induced during the immune response is IL-2. Following T cell activation, the genes encoding IL-2 and the various chains of it s receptor are transcriptionally induced. In turn, secreted IL-2 serve s to stimulate the proliferation and differentiation of T lymphocytes. Several recent studies have implicated Jak kinases in the signaling p athway induced by IL-2. Following this lead, we set out to identify tr anscription factors induced in response to IL-2. Human peripheral bloo d lymphocytes were observed to contain several IL-2-inducible DNA bind ing activities. Similar activities were also observed in a transformed human lymphocyte line, termed YT. We have purified these activities a nd found that the principal IL-2-inducible component bears significant relatedness to a prolactin-induced transcription factor first identif ied in sheep mammary gland tissue. We hypothesize that activation of t his protein, designated hStat5, helps govern the biological effects of IL-2 during the immune response.