GYPC and rheumatoid arthritis: Moreover, flow cytometry, proximity ligation assays, GYPC knockdown experiments, ELISAs using rGYPC and rORM2, and blocking experiments with soluble rGYPC all support the notion that GYPC functions as a receptor for ORM2 on RA-FLSs to mediate IL-6 and CXCL8 production, which suggests a novel proinflammatory function of GYPC.