CD8A and rheumatoid arthritis: The proinflammatory type 17-like CD103+CD69+CD8+TRM cells are specifically aggregated in the synovial fluid of PsA, whereas cytotoxic and Treg-like CD8+TRM cells are found in both RA and PsA.19 Whether the different phenotypes of TRM cells in the two arthritis attributed to the plasticity of TRM cells in different environments and the specific environmental stimulators needs further validation.