To analyze CXCR5 molecule expression in different pulmonary granulomatous tissues and to explore its differential diagnostic value between pulmonary tuberculosis and pulmonary sarcoidosis.

43 patients with lung granulomatosis were diagnosed by bronchoscopic lung tissue biopsy from the First Affiliated Hospital of Soochow University from January 2016 to December 2022. Fifteen cases of pulmonary sarcoidosis and 28 cases of pulmonary tuberculosis were comprehensively diagnosed. The expression of CXCR5 molecules in tissue sections was analyzed by immunohistochemistry. The expression of CXCR5 in CD8⁺ T cells and CD4⁺ T cells of granuloma tissue sections was analyzed by dual immunofluorescence labeling, and quantitative scoring was performed.

In pulmonary tuberculosis granuloma tissues, there were 22 cases (78.57%) with positive expression of CXCR5 greater than 2 points, 12 cases (42.86%) with expression intensity greater than 2 points, 10 cases (35.71%) with quantitative scores less than 3 points, and 8 cases (28.57%) with quantitative scores greater than 6 points. In the granuloma tissues of pulmonary sarcoidosis, there were 9 cases (60.00%) with positive expression of CXCR5 greater than 2 points, and the intensity of CXCR5 expression was less than 2 points in 15 cases(100.00%), and 11 cases (73.33%) were less than 3 points. Compared with pulmonary sarcoidosis, the expression intensity of CXCR5 molecules in pulmonary tuberculous granulomatous tissues was increased. The overall score of CXCR5 molecular expression was also increased (4.00±2.12) vs.( 2.18±1.87) (P<0.05). According to the ROC analysis, CXCR5 expression quantitative score was the best cut-off value when it was equal to 2.85 points. The AUC of the differential diagnosis of pulmonary tuberculosis and pulmonary sarcoidosis was 0.733, with a specificity of 73.3% and a sensitivity of 64.3%. Fluorescence colocalization analysis showed that the infiltration levels of follicular CD4⁺ T cells (0.7933 vs. 0.5150) and follicular CD8⁺ T cells (0.8350 vs. 0.6100) in pulmonary tuberculosis granuloma tissues were also increased compared with pulmonary sarcoidosis(P<0.05).

There are differences in the expression of CXCR5 molecule and surface-labeled follicular CD4⁺ T cells and follicular CD8⁺ T cells in granulomatous tissues of pulmonary tuberculosis and pulmonary sarcoidosis, which has differential diagnostic value.