Single-Cell Sequencing Unveils the Cellular Characteristics Underlying the Onset and Progression of Hematogenous Disseminated Tuberculosis

The etiology of hematogenous disseminated tuberculosis (DTB) likely involves multiple factors, though it remains incompletely understood. In this study, we performed single-cell RNA transcriptome and T cell receptor (TCR) sequencing on samples from 7 DTB patients. We observed a significantly elevated proportion of inflammatory immune cells (e.g., monocytes and macrophages) and a markedly decreased abundance of various lymphocytes (e.g., T cells, B cells, and plasma cells) in DTB. This suggests that lymphopenia might be a prominent feature of the disease. T cell pseudotime analysis revealed that most hypervariable gene expression decreased over time in DTB, suggesting that T cell functional exhaustion may be an immunological characteristic of DTB patients. Another important manifestation of T cell exhaustion in DTB is the significant absence of mucosal-associated invariant T (MAIT) cells, a crucial cytological feature in DTB peripheral blood. Specific polymorphisms were identified in the TCR repertoire of DTB patients, including TRAV9-2, TRAV13-1, TRBV20-1, and TRBV5-1, with dominant clones TRAJ49, TRBJ2-7, and TRBJ2-1. Analysis of complementarity determining region 3 (CDR3) revealed that the most commonly used combination was TRAV1-2/TRAJ33. Notably, a motif containing "CAAMD" was significantly reduced in DTB patients, which may indicate unique characteristics of the disease. In summary, our study offers new insights into the complex dynamic changes of TCR clonotypes, CDR3 dominant motifs, and various cell types in the pathogenesis of DTB.