Therapeutic effect of regulatory T cells on mice with experimental autoimmune encephalomyelitis

Objective To study the role of Treg cells in the development of mouse experimental autoimmune encephalomyelitis (EAE) through depleting or transplanting Treg cells. Methods C57BL/6 mice were injected with anti-CD25 monoclonal antibody to deplete natural CD25-expressing Treg cells in vivo, and then treated with MOG35-55/CFA to induce EAE. Their EAE scores were compared with those of the mice without Treg cell deletion (control group). The numbers and percentages of CD4+ Foxp3+ cells in mouse blood samples on 6 d, 10 d, 20 d and 35 d were quantified using flow cytometry. To evaluate the therapeutic effect of Treg cells transplantation on EAE, magnetic activated cell sorting (MACS) combined with fluorescence-activated cell sorting (FACS) was used to isolate Treg cells from spleen and lymph nodes of Foxp3GFP+ transgenic mice on 6 d after EAE induction. Then the cells were injected through tail vein into wild-type mice on 6 d after EAE induction. The EAE scores of both recipient and control mice were recorded and compared. Results The efficiency of natural Treg cells depletion with anti-CD25 antibody was above 95%. The mice with Treg cell depletion developed significantly more severe EAE than the control mice after MOG35-55/CFA induction. FACS analysis of Treg cells during the development of EAE demonstrated that the lowest Treg cell percentage was detected on 6 d after EAE induction, hence it was the time point for the transplantation of Treg cells. CD4+ GFP+ Treg cells were isolated from Foxp3GFP+ transgenic mice on 6 d after EAE induction and immediately transplanted into wild-type mice on 6 d after EAE induction. The transplantation of isolated Treg cells significantly alleviated the EAE in mice as compared with the control group. Conclusions Mice with Treg cell depletion developed severer EAE than the control mice after induction, but the EAE score could be significantly reduced with the transplantation of Treg cells. This study showed that the transplanted Treg cells had protective effect on mice during the course of EAE development. Thus, Treg cell transplantation could be used as an effective therapeutic approach for the treatment of multiple sclerosis (MS). Key words: Multiple sclerosis; Experimental autoimmune encephalomyelitis; Regulatory T cell