HSP90B1 and rheumatoid arthritis: In humans, Pope et al. described high levels of gp96 in synovial fluids from patients with rheumatoid arthritis (RA) compared to samples obtained from patients with osteoarthritis; the collected synovial gp96 was then shown to evoke an inflammatory response in human macrophages in the form of elevated TLR2, IL-6, and TNFα.