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

Abstract

IFN-γ-producing CD4 ⁺ T cells are required for protection against lethal Mycobacterium tuberculosis ( Mtb ) infections. However, the ability of CD4 ⁺ T cells to suppress Mtb 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 Mtb -infected mice. Although the recruited MDMs became quickly and preferentially infected with Mtb , CD4 ⁺ T cells rapidly disinfected the MDMs. Clearance of Mtb 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 Mtb control. Thus, by recruiting MDMs, CD4 ⁺ T cells initiate a cycle of bacterial phagocytosis, Mtb antigen presentation and disinfection in an attempt to clear the bacteria from the lungs.