Gamma c cytokines condition the progressive differentiation of CD4+ T cells.

After their initial antigen encounter in the secondary lymphoid organs, activated T cells must receive additional signals in the peripheral tissues to fully differentiate. Here, we provide evidence that gamma(c) cytokines are critical during this process. Using the Marilyn (Ml) T cell antigen receptor (TCR) transgenic model, we show that male skin grafts are tolerated in the absence of gamma(c), but that Ml CD4(+) T cells proliferate normally in response to antigen, traffic to the graft site and recruit an inflammatory response [including natural killer (NK) cells, neutrophils, and macrophages] that is independent of T cell gamma(c) expression.

Role for inducible costimulator in control of Salmonella enterica serovar Typhimurium infection in mice.

Inducible costimulator (ICOS) is expressed on activated T cells and plays a key role in sustaining and enhancing the effector function of CD4 T cells. Given the function of this molecule in sustaining T-cell responses, we reasoned that ICOS might play an important role in a prolonged infection model, such as Salmonella infection of mice. To test this hypothesis, wild-type (WT) and ICOS-deficient (ICOS-/-) mice were infected systemically with a Salmonella enterica serovar Typhimurium strain expressing the chicken ovalbumin gene (Salmonella-OVA).