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 Its receptor are transcriptionally induced. In turn, secreted IL-2 serves to stimulate the proliferation and differentiation of T lymphocytes. Several recent studies have implicated Jak kinasea in the signaling pathway Induced by IL-2. Following this lead, we set out to identify transcription factors Induced In response to IL-2. Human peripheral blood lymphocytes were observed to contain several IL-2-induclbie DNA binding activities. Similar activities were also observed in a transformed human lymphocyte line, termed YT. We have purified these activities and found that the principal IL-2-inducible component bears significant relatedness to a prolactin-induced transcription factor first identified in sheep mammary gland tissue. We hypothesize that activation of this protein, designated hStat5, helps govern the biological effects of IL-2 during the Immune response.