Turning the tables: Loss of adaptive immunity reverses sex differences in tuberculosis

Sex-based differences in innate immunity may play a crucial role in susceptibility to and progression of tuberculosis (TB), a disease that disproportionately affects men. This study aimed to examine whether early host-pathogen interactions contribute to the heightened vulnerability of males to Mycobacterium tuberculosis ( Mtb ) infection. Using recombination activating gene knockout (RAG KO) mice, which lack adaptive immunity, we were able to isolate and analyze innate immune responses to Mtb without the influence of T and B cells. Surprisingly, and in stark contrast to wild-type mice that reflect the male bias as observed in humans, female RAG KO mice were more susceptible to Mtb than their male counterparts. Increased lung CFU in females was accompanied by a significant rise in inflammation, indicated by elevated levels of inflammatory cytokines and chemokines, as well as a massive influx of neutrophils into the lungs. In contrast, male mice exhibited higher levels of IFN-γ and CCL5, along with a greater presence of NK cells in their lungs, suggesting that, in the absence of adaptive immunity, males benefit from a more robust NK cell response, potentially offering greater protection by better controlling inflammation and slowing disease progression.