KRT10 and rheumatoid arthritis: For instance, HERV-K10 Gag1 protein shares an antigenic region with Collagen II, which is highly expressed in joints, and Freimanis et al. demonstrated that human fibroblast-like synoviocytes derived from a RA patient displayed several fold higher expression of HERV-K10 gag1 compared to samples from osteoarthritis (OA) and healthy donors [135].