Compartment-specific inflammation in tuberculous lymphadenitis: a case-control study.

Extrapulmonary tuberculosis (EPTB) represents a substantial proportion of tuberculosis cases, particularly among people living with HIV. Tuberculous lymphadenitis is one of the most common forms of EPTB and represents a condition in which the lymph node functions both as an immune-organizing site and a focus of Mycobacterium tuberculosis (Mtb) infection. Although peripheral blood biomarkers are frequently used to investigate immune responses in tuberculosis, they may not accurately reflect immunological processes occurring at the site of disease. In this study, we aimed to characterize and compare systemic and local inflammatory responses in individuals with suspected lymph node tuberculosis. We conducted a case-control study including 24 individuals undergoing lymph node biopsy for pathological lymphadenopathy at the National Institute of Infectious Diseases Evandro Chagas (Fiocruz), Brazil. Eleven participants were diagnosed with tuberculous lymphadenitis (45.8%) and thirteen served as non-TB controls (54.2%). Paired plasma and lymph node interstitial fluid samples were collected, and concentrations of 29 cytokines, chemokines, and growth factors were quantified using multiplex Luminex assays. Statistical analyses included non-parametric comparisons, hierarchical clustering, Spearman correlation-based network analysis, and canonical correlation analysis to evaluate inflammatory profiles and immune network organization. Plasma inflammatory profiles did not distinguish EPTB cases from controls. In contrast, lymph node samples from EPTB participants exhibited significantly higher concentrations of IL-8, IL-3, and IL-5 and reduced IL-10 levels. Network analyses of correlations between protein concentrations revealed dense and highly interconnected inflammatory networks in plasma, centered on IL-6, IFN-α2, and IL-12p70, whereas lymph node networks were sparser and dominated by TNF-α and IL-1 family cytokines. Cross-compartment analysis identified associations between systemic mediators, particularly TNF-β and IL-7, and pro-inflammatory signals in lymph nodes. Additionally, HbA1c levels were correlated with concentrations of multiple inflammatory mediators, particularly within lymph nodes. Together, these findings indicate that tuberculous lymphadenitis is characterized by marked compartmentalization of immune responses, emphasizing the importance of tissue-level immune profiling for understanding EPTB pathogenesis.