Age-stratified immune characteristics in central nervous system tuberculosis patients: a comparative T lymphocyte subset analysis within a cohort of 862 extrapulmonary tuberculosis patients.

BACKGROUND

Central nervous system tuberculosis (CNS-TB) remains a critical clinical challenge with high mortality, and its underlying immunopathological mechanisms have not been fully elucidated. This study aimed to investigate age-dependent variations in T lymphocyte subsets among CNS-TB patients and their clinical implications.

METHODS

In this retrospective study, we analysed 862 patients with extrapulmonary tuberculosis (EPTB) admitted to Fuzhou Pulmonary Hospital between April 2018 and April 2024. The cohort comprised 177 CNS-TB patients and a control group of 685 non-central nervous system extrapulmonary tuberculosis (non-CNS EPTB) patients. We comprehensively compared demographic characteristics, medical history, nutritional parameters, T lymphocyte subsets (CD3+, CD4+, CD8+, and CD45+), and neutrophil-to-lymphocyte ratio (NLR) between groups, with detailed age stratification and correlation analyses.

RESULTS

Baseline characteristics, medical history, and nutritional parameters were not significantly different between the groups. CNS-TB patients exhibited markedly reduced T lymphocyte counts, which were most pronounced in the 25–54 year age group (CD3+: 735.5 vs 1010.0 cells/μL, P < 0.001; CD4+: 389.0 vs 576.0 cells/μL, P < 0.001; CD8+: 285.5 vs 358.0 cells/μL, P = 0.013; and CD45+: 1109.5 vs 1448.0 cells/μL, P < 0.001). These differences persisted but attenuated in the 55–64 years age group, with no significant disparities in the 18–24 years and ≥ 65 years age groups. Age-stratified analysis revealed a progressive NLR increase, peaking in patients ≥ 65 years (7.07 vs 4.67, P = 0.010), with diminishing intergroup differences. Correlation analysis revealed strong positive correlations among T-lymphocyte subsets (r = 0.52–0.96, P < 0.001), significant positive correlations with lymphocyte counts (r = 0.52–0.71, P < 0.001) and moderate negative correlations with the NLR (r = − 0.27– -0.37, P < 0.001).

CONCLUSION

CNS-TB patients display characteristic T lymphocyte depletion and elevated NLRs, with dynamic age-dependent immune characteristics most prominent in immunocompetent adults. Lymphocyte counts can predict T-cell subset levels, whereas NLR values can predict inflammatory and immune response states. This study provides the first comprehensive demonstration of age-dependent immune characteristics in CNS-TB patients, offering a theoretical foundation for age-stratified immune monitoring strategies. CLINICAL TRIAL NUMBER: Not applicable.