Interleukin 7 receptor-deficient mice lack gamma delta T cells

The interleukin 7 receptor (IL-7R) plays a crucial role in early B- and T-cell development. It consists of a unique alpha chain and a common gamma chain [IL-2 receptor gamma chain (IL-2R gamma)]. Gene inactivation of IL-7, IL-7R, and IL-2R gamma resulted in severe impairment of B and T lymphopoiesis in mice. In addition, IL-2R gamma-deficient mice lack gamma delta T cells in the skin and have the impaired development of natural killer (NK) cells and intraepithelial lymphocytes. To explore the role of IL-7/IL-7R system in gamma delta T- and NK-cell development, we have generated and analyzed IL-7R-deficient mice. gamma delta T cells were absent from skin, gut, liver, and spleen in the deficient mice. In contrast, alpha beta T and B cells were detected in reduced, but certain, numbers, and NK cells developed normally, The gamma delta T-cell development in fetal and adult thymus was also completely blocked. These results clearly demonstrate that the signal from IL-7R is indispensable for gamma delta T-cell development in both thymic and extrathymic pathways. On the contrary, it is suggested that NK-cell development requires cytokine(s) other than IL-7.