CD4 and chlamydia infectious disease: Despite this deficiency, CD4-Cre/IFN-γ-flox/flox chimeras resolved Chlamydia infection similarly to non-Cre expressing chimeras (Fig 8B and 8C) and did not develop systemic bacterial infection, as no bacteria were detected in spleen, lung, or kidney of mice on day 21 (n = 5 per group), demonstrating that IFN-γ from CD4 T cells is not an essential component of Chlamydia immunity in the FRT.