Distinctive Immuno-Inflammatory Pattern in Tuberculous Lymphadenitis: A Retrospective Cohort Study with Propensity Score Matching.

Purpose: Tuberculous lymphadenitis (TBL) represents a common form of extrapulmonary tuberculosis (EPTB), yet its immunological characteristics compared to other EPTB forms remain poorly characterized. We aimed to compare immunological parameters between TBL and non-TBL patients to elucidate site-specific immune phenotypes.

Patients And Methods: We conducted a retrospective single-center study at Fuzhou Pulmonary Hospital, China (April 2018-April 2024). From 1,408 EPTB patients screened, 862 met inclusion criteria after excluding immunocompromised patients, those with incomplete data, or age <18 years. Patients were stratified into TBL (n=337) and non-TBL EPTB (n=525) groups. To mitigate confounding, we implemented 1:1 propensity score matching based on demographic factors (age, sex) and nutritional status (BMI, hemoglobin, albumin), yielding 323 matched pairs. We compared inflammatory markers (neutrophil count, neutrophil-to-lymphocyte ratio [NLR]) and immunological parameters (lymphocyte count and T lymphocyte subsets: CD3+, CD4+, CD8+, CD45+) between groups using Mann-Whitney -tests and Spearman correlation analyses.

Results: In matched cohorts, TBL patients demonstrated markedly higher lymphocyte counts than non-TBL patients (1.27 vs 1.04×10/L, <0.001) despite comparable neutrophil counts (4.45 vs 4.49×10/L, =0.724), resulting in significantly lower NLR (3.58 vs 4.38, =0.001). T lymphocyte subset analysis revealed substantially elevated absolute counts in TBL patients: CD3+ (1000.00 vs 829.00 cells/μL, <0.001), CD4+ (555.00 vs 474.00 cells/μL, =0.007), CD8+ (372.00 vs 305.00 cells/μL, <0.001), and CD45+ (1393.00 vs 1196.00 cells/μL, <0.001). Lymphocyte counts strongly positively correlated with all T cell subsets (CD3+: =0.72, CD4+: =0.72, CD8+: =0.55; all <0.001), while higher NLR values were associated with lower T cell subset counts.

Conclusion: TBL patients exhibit distinctive immunological characteristics, including lower NLR values and elevated T lymphocyte subset counts compared to other EPTB forms. These findings provide novel insights into site-specific immune responses to Mycobacterium tuberculosis infection, enhancing our understanding of the pathophysiological mechanisms underlying different manifestations of tuberculosis.