To investigate the role of glycoprotein A repetitions predominant (GARP) in the pathogenesis of tuberculosis through regulatory T cell (Treg), in order to provide new targets for the treatment of tuberculosis.

Sixty patients with active pulmonary tuberculosis (ATB) admitted to Huashan Hospital, Fudan University and Wuxi Fifth People′s Hospital from January to September 2021 were included. And six individuals with latent tuberculosis infection (LTBI), and 16 healthy controls (HC) were recruited during the same period. Flow cytometry was performed to detect the proportion of Treg in the peripheral blood, and the expressions of GARP and transforming growth factor-β1 (TGF-β1) on Treg in different groups. Mann-Whitney U test was used for statistical analysis.

Among the 60 patients with ATB, 23 patients did not receive anti-tuberculosis drug therapy, 17 patients were treated for less than three months, ten patients were treated for three to less than six months, and ten patients were treated for greater than or equal to six months. The percentage of CD4⁺ CD25⁺ forkhead box protein 3 (Foxp3)⁺ Treg in untreated ATB patients was 7.50%(5.67%, 9.00%), which was higher than that in HC (5.57%(5.03%, 6.09%)), and the difference was statistically significant (U=95.00, P=0.010). The percentage of GARP expressing in CD4⁺ CD25⁺ Foxp3⁺ Treg in untreated ATB patients was 10.37%(7.79%, 12.90%), which was higher than that in LTBI (7.02%(5.15%, 8.81%)) and HC (5.33%(4.26%, 6.67%)), respectively, and the differences were both statistically significant (U=31.00, P=0.040; U=36.00, P<0.001, respectively), while there was no significant difference between LTBI and HC (U=25.00, P=0.095). The percentage of CD4⁺ CD25⁺ Foxp3⁺ Treg expressing TGF-β1 in untreated ATB patients was 7.13%(4.25%, 8.89%), which was higher than that in HC (3.59%(2.10%, 5.17%)), and the difference was statistically significant (U=71.00, P=0.001). The expressions of GARP in CD4⁺ CD8^-CD25⁺ Foxp3⁺ Treg in patients with ATB treated for less than three months group, three to less than six months group and greater than or equal to six months group were 7.82%(3.94%, 13.17%), 6.92%(5.61%, 9.47%) and 7.26%(5.82%, 9.64%), respectively. The expressions of TGF-β1 in CD4⁺ CD8^-CD25⁺ Foxp3⁺ Treg in the above three treatment groups were 11.16%(7.91%, 15.23%), 8.66%(5.43%, 12.54%) and 7.82%(6.01%, 9.53%), respectively, and the expression of TGF-β1 in CD4⁺ CD8^-CD25⁺ Foxp3⁺ Treg in the patients with ATB treated for less than three months group was higher than that in the greater than or equal to six months group, the difference was statistically significant (U=37.50, P=0.024).

Foxp3/GARP/TGF-β1 pathway may be involved in the immune mechanism of Treg regulating the pathogenesis of tuberculosis, and GARP may be a new target for anti-tuberculosis therapy.

Glycoprotein A repetitions predominant; Transforming growth factor beta; Regulatory T cells; Active tuberculosis; Immune