Together, we conclude that the protective anti-viral CD8+ T cell response in GITRL tg mice is fully dependent on CD4+ T cells, suggesting that although direct GITR triggering on CD8+ T cells might account for some increase in T cell function, it is not sufficient to clear the virus and prevent CD8+ T cell exhaustion in this model of chronic viral infection. The gene discussed is TNFRSF18; the disease is viral infectious disease.