Interleukin 33 ameliorates disturbance of regulatory T cells in pulmonary sarcoidosis

The feature of pulmonary sarcoidosis is characterized by a Th1/Th17/regulatory T cells (Tregs) -driven inflammatory process in lung, resulting in noncaseating granulomas containing CD4+ T cells. Tregs increase in both lung and peripheral blood, with damaged immunoregulatory function. The current study investigated the effects of IL33 or anti-IL23 antibody on restoring the homeostasis and functions of Tregs in mycobacterial superoxide dismutase A (SodA)-induced pulmonary sarcoidosis. IL33 or anti-IL23 antibody was administered to mice with late-stage pulmonary sarcoidosis. The levels of Th1/Th17/Tregs and Tregs' suppressive functions were detected by fluorescence activated cell sorting (FACS) analysis or qPCR. The expressions of key proteins in PI3K/Akt/mTOR and TGF-β/Smad2/Smad3 signaling pathways were tested by western blot. IL33 administration was associated with the rebalance of Th1/Th2 and Tregs, as well as a superior suppressor activity of Tregs on effector T cells in sarcoidosis, probably through increasing ST2 expressions on Tregs, along with the suppression of PI3K/Akt/mTOR and TGF-β/Smad2/Smad3 signaling pathways. Small dose of anti-IL23 antibody independently improved Th1/Th2 bias, but had limited effects on the homeostasis and ST2 expressions on Tregs. These results suggested a major anti-inflammatory ability of IL33 to ameliorate the disturbance of Th1/Th2 and Tregs in pulmonary sarcoidosis, and provided rationales for further strategies of targeting the IL33/ST2 signals in the treatment of pulmonary sarcoidosis.