The key role of IL-7 in lymphopoiesis.

In mice, interleukin 7, although initially thought to be predominantly a cytokine acting on B cells, appears to have potent survival and growth activity during both B and T lymphopoiesis. Although acting on both lineages at the very immature stages, T cell differentiation becomes independent of IL-7 at the intermediate stages before regaining dependence on IL-7 for survival and proliferation at the mature T cell stage. In contrast, although essential for B lymphopoiesis, mature B cell survival is independent of IL-7. In this review, we focus on and discuss the similarities and differences between the role of IL-7 in these two processes.