Natural killer cells and mast cells from gp49B null mutant mice are functional

Immune responses are controlled by a combination of positive and negative c ellular signals. Effector cells in the immune system express inhibitory rec eptors that serve to limit effector cell expansion and to protect the host from autoreactivity. gp49B is a receptor of unknown function that is expres sed on activated mast cells and natural killer (NK) cells and whose cytopla smic tail endows it with inhibitory potential. To gain insight into the fun ction of gp49B in mice, we disrupted the gp49B gene by homologous recombina tion. gp49B(0) mice were born at expected ratios, were healthy and fertile, and displayed normal long-term survival rates. gp49B(0) mice showed no def ect in NK or mast cell development. Furthermore, NK and mast cells from the gp49B(0) mice showed activation properties in vitro similar to those of ce lls isolated from wild-type mice. Therefore, gp49B is not critical for the development, expansion, and maturation of mast cells and NK cells in vivo. The healthy status of gp49B(0) mice makes them suitable for testing the rol e of gp49B in immune responses to infectious agents.