Sex-specific transcriptional regulation in lung macrophages during sub-acute <i>Mycobacterium tuberculosis</i> infection

Biological sex significantly influences susceptibility to tuberculosis (TB), with males typically experiencing a greater disease burden than females. However, the mechanisms underlying sex-specific immune regulation during TB pathogenesis remain incompletely understood. In this study, we examined sex-based differences in pulmonary immune cell composition, inflammatory signaling pathways, and macrophage transcriptomic responses in C57BL/6 mice infected with the <i>Mycobacterium tuberculosis</i> (<i>Mtb</i>) HN878 strain during the sub-acute stage of infection. Our results show that female mice had significantly lower pulmonary <i>Mtb</i> burdens and enhanced protein kinase B (AKT)-interferon gamma (IFN-γ) signaling, which is associated with autophagy, lysosomal activation, and effective intracellular bacterial clearance. In contrast, male mice exhibited higher bacterial loads and elevated IL-6 signaling, a pathway linked to exacerbated inflammation and impaired pathogen control. Histological analysis revealed greater lymphocytic aggregation in female lungs, despite comparable levels of pulmonary macrophages between sexes. Importantly, transcriptomic profiling of lung macrophages uncovered distinct sex-specific gene expression patterns, wherein female macrophages upregulated genes involved in tissue remodeling, phagocytosis, autophagy/lipophagy, and cell survival, whereas male macrophages showed enrichment of genes related to pro-inflammatory and adaptive immune responses. Notably, male macrophages expressed higher levels of <i>Ighg1</i> (Immunoglobulin Heavy Constant Gamma 1), suggesting a potential sex-dependent modulation of humoral immunity during TB. Together, these findings demonstrate that biological sex shapes immune cell programming and host-pathogen interactions during TB, underscoring the importance of incorporating sex as a biological variable in TB research and therapeutic development.IMPORTANCEMen and women often respond differently to diseases like tuberculosis (TB), with men typically facing more severe illness, though the underlying reasons are unclear. To this end, our study investigated how male and female mice combat TB infection at a cellular and molecular level. We discovered that female mice controlled TB more effectively, as their immune systems activated specific pathways to break down and clear bacteria efficiently. Conversely, male mice showed higher bacterial loads and triggered more inflammatory, yet less effective, immune responses. Crucially, despite similar numbers of key immune cells (macrophages) in the lungs, their functional responses differed significantly by sex. These findings underscore that biological sex profoundly impacts the immune system's fight against TB, paving the way for more personalized treatments and improved outcomes for all.