IL‐35 is a novel cytokine with therapeutic effects against collagen‐induced arthritis through the expansion of regulatory T cells and suppression of Th17 cells

Abstract

Epstein‐Barr virus‐induced gene 3 (EBI3) and the p35 subunit of IL‐12 have been reported to form a heterodimeric hematopoietin in human and mouse. We have constructed a heterodimeric protein covalently linking EBI3 and p35, to form a novel cytokine which we now call IL‐35. The Fc fusion protein of IL‐35 induced proliferation of murine CD4 + CD25 + and CD4 + CD25 – T cells when stimulated with immobilized anti‐CD3 and anti‐CD28 antibodies in vitro . The IL‐35‐expanded CD4 + CD25 + T cell population expressed Foxp3 and produced elevated levels of IL‐10, whereas the IL‐35‐induced CD4 + CD25 – T cells produced IFN‐γ but not IL‐4. The in vitro expanded CD4 + CD25 + T cells retained their suppressive functions against CD4 + CD25 – effector cells. Furthermore, when cultured with soluble anti‐CD3 antibody and antigen‐presenting cells, IL‐35 suppressed the proliferation of CD4 + CD25 – effector cells. Moreover, IL‐35 inhibited the differentiation of Th17 cells in vitro . In vivo , IL‐35 effectively attenuated established collagen‐induced arthritis in mice, with concomitant suppression of IL‐17 production but enhanced IFN‐γ synthesis. Thus, IL‐35 is a novel anti‐inflammatory cytokine suppressing the immune response through the expansion of regulatory T cells and suppression of Th17 cell development.