In contrast, we found that ICOS-YF mice were substantially better than ICOS-KO mice in controlling Chlamydia. Importantly, the differences in the capacity to control Chlamydia infection between genotypes did not correlate with the magnitude of Th1/IFN-γ responses, but rather correlated with IL-17/Th17 responses. The gene discussed is ICOS; the disease is chlamydia infectious disease.