Nuclear Factor κB Signaling Deficiency in CD11c-Expressing Phagocytes Mediates Early Inflammatory Responses and Enhances <i>Mycobacterium tuberculosis</i> Control

Early innate immune responses play an important role in determining the protective outcome of Mycobacterium tuberculosis (Mtb) infection. Nuclear factor κB (NF-κB) signaling in immune cells regulates the expression of key downstream effector molecules that mount early antimycobacterial responses. Using conditional knockout mice, we studied the effect of abrogation of NF-κB signaling in different myeloid cell types and its impact on Mtb infection. Our results show that the absence of IKK2-mediated signaling in all myeloid cells resulted in increased susceptibility to Mtb infection. In contrast, the absence of IKK2-mediated signaling in CD11c+ myeloid cells induced early proinflammatory cytokine responses, enhanced the recruitment of myeloid cells, and mediated early resistance to Mtb. Abrogation of IKK2 in MRP8-expressing neutrophils did not affect disease pathology or Mtb control. Thus, we describe an early immunoregulatory role for NF-κB signaling in CD11c-expressing phagocytes and a later protective role for NF-κB in LysM-expressing cells during Mtb infection.