TIGIT reverses IFN-α-promoted Th1-like Tregs via in-sequence effects dependent on STAT4

The induction direction of interferon (IFN)-α in T-cell phenotype and function varies depending on the activation state of the cell and the time of stimulation. To assess the effects of elevated IFN-α on regulatory T cells (Tregs) in systemic lupus erythematosus (SLE) patients, we investigated the differentiation of Th1-like Tregs under in-sequence and out-of-sequence conditions and the reversal effect of activating TIGIT on immune suppression.

Phenotypes and activation levels of Tregs from SLE patients and healthy controls were analyzed using flow cytometry. In vitro culture conditions based on the sequence of TCR activation and IFN-α stimulation simulated in-sequence or out-of-sequence effects. CD4⁺T cells and Tregs were cultured under the above conditions with or without TIGIT agonist. Expression of related characteristic markers and phosphorylation levels of AKT, mTOR, and STATs were detected using flow cytometry and ELISA.

The frequency of Th1-like Tregs and activation levels of Tregs increased, but TIGIT expression in Tregs decreased in SLE patients. IFN-α promoted the conversation of Tregs to Th1-like Tregs while reducing immunosuppressive function under in-sequence conditions. The STAT4 pathway, but not the STAT1 pathway, was crucial for the IFN-α-mediated in-sequence effects. Reactivation of TIGIT reversed Th1 polarization of Tregs by suppressing AKT/mTOR and STAT4 signaling.

Our findings suggest that IFN-α mediated in-sequence effects on Tregs may be responsible for the expansion of Th1-like Tregs in SLE. TIGIT can restore immune suppression damage in Tregs and represents a potential therapeutic target for SLE.