Skint8, a Novel B7 Family-Related Molecule, Negatively Regulates T Cell Responses

Immune responses are tightly controlled by T cell costimulatory and coinhibitory molecules. In this study, we identify Skint8 as a new member of the T cell coinhibitory group, whose extracellular domains share significant homology with existing B7 family members. Skint8 mRNA is expressed in resting and activated B cells, monocytes, and CD4 T cells. The Skint8 putative receptor is expressed on activated CD4 and CD8 T cells, B cells, monocytes and dendritic cells. Recombinant Skint8-IgG Fc fusion protein inhibits T cell proliferation, activation, and cytokine production in vitro. In vivo administration of Skint8-IgG Fc reduces T cell activation and alleviates experimental autoimmune encephalomyelitis in mice. The findings broaden our understanding of the regulation of immune responses and may have implications for treating immune-related diseases.