CD4 T cells recruit, then engage macrophages in cognate interactions to clear from the lungs.

IFN-γ-producing CD4 T cells are required for protection against lethal ( ) infections. However, the ability of CD4 T cells to suppress growth cannot be fully explained by IFN-γ or other known T cell products. In this study, we show that CD4 T cell-derived IFN-γ promoted the recruitment of monocyte-derived macrophages (MDMs) to the lungs of -infected mice. Although the recruited MDMs became quickly and preferentially infected with , CD4 T cells rapidly disinfected the MDMs. Clearance of from MDMs was not explained by IFN-γ, but rather by MHCII-mediated cognate interactions with CD4 T cells. These interactions promoted MDM expression of glycolysis genes essential for control. Thus, by recruiting MDMs, CD4 T cells initiate a cycle of bacterial phagocytosis, antigen presentation and disinfection in an attempt to clear the bacteria from the lungs.