MO243STUDY ON THE EFFECT AND MECHANISM OF NOVEL REGULATORY T CELL (CD4+CD126LOWFOXP3+ TREG) IMMUNOTHERAPY IN LUPUS NEPHRITIS*

Abstract Background and Aims Our previous study found a new regulatory T cell subpopulation, CD4+CD126lowFoxp3+ regulatory T cells (CD4+CD126lowFoxp3+ Treg). This cell can maintain a stable immune regulatory function in the inflammatory state. Through in vivo and in vitro experiments, we have confirmed that CD4+CD126lowFoxp3+ Treg has an immunotherapeutic effect on T cell-mediated mouse models of autoimmune diseases such as colitis and collagen-induced arthritis (CIA). Further experimental studies showed that CD4+CD126lowFoxp3+ Treg could reduce the kidney injury caused by autoantibodies and prolong the survival time of lupus mice. However, the mechanism of CD4+CD126lowFoxp3+ Treg immunotherapy in lupus nephritis is not clear. The purpose of this study was to explore the mechanism of CD4+CD126lowFoxp3+ Treg immunotherapy in mice with lupus nephritis. Method In vitro experiments CD4+CD126lowFoxp3+ Treg or CD4+CD126lowFoxp3+ Treg pretreated with PD-1 inhibitor were co-cultured with T or B lymphocytes of lupus mice under different in vitro culture condition. The expression levels of Akt and mTOR of Treg in each group were measured under immunoinflammatory conditions. To observe the effects and differences of Treg groups on the activation, proliferation and differentiation of T or B cells and other immunomodulatory effects. In vivo experiments CD4+CD126lowFoxp3+ Treg (2 × 106/mouse) and CD4+CD126lowFoxp3+ Treg (2 × 106/mouse) pretreated with PD-1 inhibitor and PBS were injected into NZM2328 lupus mice, respectively. After cell injection, urine protein was measured weekly. Autoantibody expression in lupus mice was measured every two weeks. The effects of Treg on the proliferation and differentiation of T/B cells in lupus mice were observed. The therapeutic effects of Treg on lupus mice were observed. Results Compared with CD4+CD126lowFoxp3+ Treg, the expression of Akt and mTOR increases in PD-1 inhibitors pretreatment cells. The activation, proliferation and differentiation functions of T or B lymphocytes of lupus mice were significantly weakened by immunosuppression of PD-1 inhibitors pretreated Treg in vitro, indicating that CD4+CD126lowFoxp3+ Treg may inhibit Akt-mTOR signaling pathway through PD-1 in in vitro. Compared with CD4+CD126lowFoxp3+ Treg, the activation, proliferation and differentiation functions of T or B lymphocytes of lupus mice were significantly weakened by immunosuppression of PD-1 inhibitors pretreated Treg in vivo. And its therapeutic effect on lupus mice was ineffective, indicating that CD4+CD126lowFoxp3+ Treg may inhibit Akt-MTOR signaling pathway through PD-1 in vivo. Conclusion CD4+CD126lowFoxp3+ Treg may inhibit the Akt-mTOR signaling pathway by expressing PD-1, and maintain stable immunomodulatory function in the inflammatory state, thus producing immunotherapeutic effect on lupus nephritis mice.