Cutting Edge: IL-1R1 Mediates Host Resistance to <i>Mycobacterium tuberculosis</i> by <i>Trans</i>-Protection of Infected Cells

Abstract

Abstract IL-1R1 deficiency in mice causes severe susceptibility to Mycobacterium tuberculosis. Mice and macrophage cultures lacking IL-1R1 display increased bacterial growth, suggesting that phagocytes may require IL-1R1–dependent antimicrobial signals to limit intracellular M. tuberculosis replication directly. However, the myeloid-cell–intrinsic versus –extrinsic requirements for IL-1R1 to control M. tuberculosis infection in mice have not been directly addressed. Using single-cell analysis of infected cells, competitive mixed bone marrow chimeras, and IL-1R1 conditional mutant mice, we show in this article that IL-1R1 expression by pulmonary phagocytes is uncoupled from their ability to control intracellular M. tuberculosis growth. Importantly, IL-1R1–dependent control was provided to infected cells in trans by both nonhematopoietic and hematopoietic cells. Thus, IL-1R1–mediated host resistance to M. tuberculosis infection does not involve mechanisms of cell-autonomous antimicrobicidal effector functions in phagocytes but requires the cooperation between infected cells and other cells of hematopoietic or nonhematopoietic origin to promote bacterial containment and control of infection.