Reduced CD27 Expression on Antigen-Specific CD4+ T Cells Correlates with Persistent Active Tuberculosis

CD27, a member of the tumor necrosis factor receptor family, has important role in generation of T cell immunity. In this study, association of CD27 expression on mycobacterial antigen-specific CD4(+) T cells with pulmonary tuberculosis (TB) was investigated. Mycobacterial antigen-specific CD4(+) T cells were identified based on CD154 expression and CD27 expression on antigen-specific CD4 T cells was analyzed by flow cytometry. Compared with tuberculin-positive controls, patients with bacterial culture-positive pulmonary TB had significantly reduced CD27 expression on antigen-specific CD4 T cells. The persistent active TB patients had much lower percentages of CD27(+) antigen-specific CD4 T cells than culture-positive new TB patients (P = 0.008) and healthy controls (P = 0.005). Logistic regression analysis on frequencies of CD27-expressing antigen-specific CD4 T cells and TB patients' clinical characteristics indicated that low percentage of CD27(+) antigen-specific CD4 T cells correlated significantly with persistent active tuberculosis (P = 0.002, odds ratio = 19.6). It is concluded that frequency of CD27(+) antigen-specific CD4 T cells could be used as an immunological marker for persistent active TB.