Growth Factors can Enhance Lymphocyte Survival without Committing the Cell to Undergo Cell Division

Growth factors have been defined by their ability to promote the proliferative expansion of receptor-bearing cells. For example, antigen-activated T cells expressing the αβγ form of the interleukin 2 (IL-2) receptor will proliferate in response to IL-2. In contrast, resting T cells, which express the IL-2 receptor β and γ chains, do not proliferate in response to IL-2. We demonstrate that the survival of resting T cells following γ irradiation is greatly enhanced by pretreatment with IL-2. The radioprotective effect of IL-2 is dose dependent, does not result from the induction of cell proliferation, and does not require expression of the IL-2 receptor α chain. Thus, the βγ IL-2 receptor expressed on resting T cells can transduce signals that promote cell survival without committing the T cell to undergo cell division. IL-4 and IL-7, but not IL-1, IL-3, or IL-6, were also found to enhance the survival of quiescent T cells following γ irradiation. Thus, certain growth factor-receptor interactions can serve to maintain cell viability in a manner that is independent of their ability to initiate or maintain cell proliferation. These data may have important implications for the use of growth factors in patients being treated with radiation and/or chemotherapy.