Single-Cell Immune Profiling Reveals Non-classical Monocyte-Driven Immunodepression in Tuberculosis Treatment Non-Responders

Sputum culture conversion (SCC) at 2 months is a critical predictor of tuberculosis (TB) treatment outcomes, yet the underlying immune alterations driving treatment non-response remain unclear. We performed single-cell RNA sequencing on peripheral blood mononuclear cells from 8 TB patients, stratified by 2-month SCC status, to characterize cellular heterogeneity and intercellular communication. Treatment non-responders exhibited marked expansion and terminal differentiation of non-classical monocytes with elevated TB progression risk signatures. These cells showed reduced outgoing but enhanced incoming signaling, prominently via IL-16 and TRAIL pathways, potentially amplifying regulatory T cell (Treg)-mediated immunosuppression. CD4 Tregs in non-responders engaged in intensified GALECTIN signaling toward CD8 cytotoxic T cells and mature NK cells, contributing to effector cell exhaustion. NK cell subsets, particularly mature NK c2, displayed increased inhibitory receptor expression and terminal differentiation states. Our findings delineate a dysregulated "non-classical monocyte -Treg -cytotoxic lymphocyte" axis in TB treatment failure, highlighting candidate biomarkers and host-directed therapeutic targets.