Jagged1 suppresses collagen-induced arthritis by indirectly providing a negative signal in CD8+ T cells.

Distinct Notch ligands possess a characteristic ability in terms of functional T cell differentiation. However, the precise role or the therapeutic potential of each Notch ligand in autoimmune diseases is largely unknown. In this study, we examined whether Jagged1 modulates a collagen-induced rheumatoid arthritis (CIA) model by altering T cell responses. The injection of a soluble Jagged1-encoding plasmid, sJag1-P, before or even after initial type II collagen (CII) immunization suppressed the disease severity of CIA. However, this treatment did not suppress CII-specific CD4(+) T cell proliferation and CII-specific Ab production. Depletion of either CD4(+) or CD8(+) T cells ameliorated CIA severity and sJag1-P further improved CIA in CD4(+) but not CD8(+) T cell-depleted mice. Injection of OVA and Jagged1-encoding plasmids inhibited proliferation of OVA-specific granzyme B-producing CD8(+) T cells, although Jagged1 could not directly inhibit CD8(+) T cell proliferation in vitro. The blockade of Jagged1 by an anti-Jagged1 Ab exacerbated CIA, whereas this effect was not observed in the absence of CD8(+) T cells. These data indicate that Jagged1 is able to deliver an indirect negative signal into CD8(+) T cells in vivo, which suggests its therapeutic potential in the treatment of CD8(+) T cell-mediated diseases, including rheumatoid arthritis.