Autoantigen and IL-2 activated CD4CD25T regulatory cells are induced to express CD8 and are autoantigen specific in inhibiting experimental autoimmune encephalomyelitis.

Experimental autoimmune encephalomyelitis (EAE) induced by immunization with myelin basic protein (MBP) is a self-limiting disease model of multiple sclerosis. CD4CD25Foxp3T cells play a role in limiting autoimmune disease but treatment with antigen naïve CD4CD25 cells does not reduce EAE. This study examined if in vitro activation by MBP and rIL-2 induced CD4CD25Foxp3 cells that could inhibit EAE. Culture of CD4CD8CD25cells from naïve rats with MBP and rIL-2 induced activated Treg that reduced the severity of clinical EAE and infiltration of CD8T cells and macrophage into brain stem. CD4CD25T cells activated by an irrelevant autoantigen and rIL-2 did not suppress EAE. Resting CD4CD25T cells activated by autoantigen and rIL-2 have mRNA for Infgr, Il12rb2, Il5 but not Tbet, Gata3, Ilr5ra or Ifng. These changes in mRNA expression are the markers of Ts1 cells. A proportion of CD4CD8CD25 cells activated by MBP/rIL-2 were induced to express CD8α, CD8β and CD62L. Depletion of CD4CD8αCD25 cells removed the capacity of MBP and rIL-2 activated CD4CD25T cells to suppress EAE. This study demonstrated that in vitro activation of CD4CD8CD25 cells by MBP/rIL-2 induced relevant antigen-specific Treg within days, which expressed CD8α, CD8β and CD62L with a Ts1 phenotype and that had greater potency than freshly isolated antigen naive CD4CD25Treg in suppressing clinical severity of EAE and immune inflammation in CNS. These findings may guide development of antigen-specific Treg for therapy.