Distribution and clinical significance of circulating CD8+CD28- regulatory T cells in the peripheral blood of patients with pulmonary tuberculosis

Background Regulatory T cells (Treg cells) in the peripheral blood of patients with pulmonary tuberculosis (PTB) may be closely related to the progression of PTB. In this study, the distribution characteristics and clinical importance of CD8(+)CD28(-) Treg cells in patients with tuberculosis were systematically analyzed, and the role and importance of CD8(+)CD28(-) Treg cells in influencing the immune response and progression of tuberculosis were discussed, which will provide immunological indices and reference values for the clinical diagnosis of tuberculosis. Methods Flow cytometry, sputum smears and computed tomography imaging were used to analyze the distribution characteristics of CD8(+)CD28(-) Treg cells in the peripheral blood of patients with PTB and the correlation between CD8(+)CD28(-)Treg cells and clinical and immune indices. Results The percentages of CD4(+)CD25(high) and CD8(+)CD28(-) Treg cells in the peripheral blood of patients with PTB were significantly higher than those in the healthy control (HC) group. Further analysis showed that the percentage of CD4(+)CD25(high)Treg cells in the Stage II group was significantly higher than that in the HC group. The percentages of CD4(+)CD25(high) and CD8(+)CD28(-) Treg cells increased significantly in patients in the Stage II group. The proportion of CD8(+)CD28(-) Treg cells was directly proportional to the degree of positivity in sputum smears, while CD4(+)CD25(high)Treg cells did not exhibit this trend. The correlations between the percentage of CD4(+)CD25(high) and CD8(+)CD28(-) Treg cells and the percentage of lymphocyte subsets were examined. The percentage of CD8(+)CD28(-) Treg cells was negatively correlated with the percentage of CD4(+)T cells and positively correlated with the CD8(+)T cell percentage in the HC and PTB groups. The percentage of CD4 + CD25(high)Treg cells was positively correlated with the percentage of CD4(+)T cells only in the PTB group. Conclusions This study was the first to show that the proportion of CD8(+)CD28(-) Treg cells in the peripheral blood of patients with PTB was significantly increased, and the increase in CD8(+)CD28(-) Treg cells was related to the progression of PTB, which may affect the proportion of immune cell subsets by inhibiting the immune response, resulting in the progression of PTB.