VSIG4 (V-set and immunoglobulin domain-containing protein 4), also known as CRIg (complement receptor of the immunoglobulin superfamily), is a B7 family-related transmembrane protein predominantly expressed on tissue-resident macrophages, including Kupffer cells in the liver and macrophages in inflamed tissues. It functions as a complement receptor that binds to complement components C3b and C3c, facilitating pathogen clearance and phagocytosis. Additionally, VSIG4 acts as a co-inhibitory ligand, suppressing T-cell activation by interacting with an unknown receptor on T cells, thereby contributing to immune tolerance and homeostasis.
VSIG4 antibodies are tools or therapeutic candidates designed to target this protein. Antagonistic antibodies blocking VSIG4 aim to disrupt its immunosuppressive signaling, potentially enhancing antitumor immune responses in cancers where VSIG4 is overexpressed in tumor-associated macrophages. Conversely, agonistic antibodies may exploit VSIG4’s immunoregulatory properties to dampen excessive inflammation in autoimmune diseases like rheumatoid arthritis or inflammatory bowel disease. Research also explores VSIG4's role in modulating the tumor microenvironment, with combination therapies involving PD-1/PD-L1 inhibitors being investigated.
Despite its therapeutic potential, VSIG4’s dual roles in immune activation and suppression necessitate precise targeting strategies. Current studies focus on elucidating its ligand-receptor interactions and tissue-specific functions to optimize antibody-based interventions.