Physiologic roles of interleukin-2, interleukin-4, and interleukin-7

The use of gene targeting techniques has led to new insights into the physiologic function of lymphoid growth factors, their receptors, and associated signal transduction molecules in the formation and function of T and B cells. Mice rendered deficient for the growth factors interleukin-2 or interleukin-4 exhibit impairment in certain immune responses and in steady-state immune function, although production and expansion of lymphocyte populations is unaffected. In contrast, mice deficient for interleukin-7 show a severe lymphopenia in most lymphoid tissues. Interleukin-2, interleukin-4, and interleukin-7 all utilize the common gamma (gamma c) receptor component at the cell surface of lymphocytes and the Jak3 kinase molecule to transduce signals inside the cell. Both gamma c- and Jak3 kinase-deficient animals display a phenotype similar to interleukin-7-deficient animals in terms of lymphoid development. Collectively, these genetic experiments clearly define different in vivo roles for these lymphoid factors. Interleukin-2 and interleukin-4 function by influencing mature lymphocyte populations during immune responses, whereas interleukin-7 plays a singularly dominant role, in terms of the ligands that bind to the gamma c receptor, for the production and expansion of lymphocytes.