ILC2s induce Treg but not Th2-type immunity through IL-33/ST2 pathway in pulmonary tuberculosis

Introduction: We investigated the function of type 2 innate lymphoid cells (ILC2s) and IL-33 in pulmonary tuberculosis (PTB). Methodology: Peripheral blood samples were collected from PTB patients and healthy controls. The cytometric bead array was used to detect plasma IL-33, TGF-13, IL-4, IL-5, IL-6, IL-10, IL-13, and soluble ST2 (sST2). ILC2s, Th2, and Treg cells were detected with flow cytometry. Quantitative real-time PCR was used to measure mRNA levels. ILC2s were co-cultured with peripheral blood mononuclear cells and then intervened with IL-33 or anti-ST2 antibody + IL-33 in vitro. IL-4, IL-6, IL-5, IL-10, IL-13, and TGF-13 levels were measured by enzyme-linked immunosorbent assay. Results: Compared with healthy controls, the levels of IL-33, sST2, TGF-13, IL-10, and IL-6 in the plasma of PTB patients were significantly higher. No significant difference was found in the plasma IL-4, IL-5, and IL-13 levels. Patients with PTB had significantly increased ILC2s proportion and mRNA levels of RAR-related orphan receptor alpha and GATA binding protein 3. After 48 h of IL-33 stimulation in vitro, Treg cell proportion significantly increased and the IL-10 level was significantly elevated. Treatment with anti-ST2 abolished these effects. No significant difference was found in cytokines of IL-4, IL-6, IL-5, IL-13, and TGF-13, or Th2 cells before and after IL-33 treatment. ILC2s proportion in peripheral blood was increased and plasma IL-33 was upregulated in PTB patients. Conclusions: IL-33 may promote the growth of ILC2s and the production of Treg-related cell cytokines, but not Th2-related cell cytokines, to participate in immune response to PTB.