CD4 and rheumatoid arthritis: IL-17 is mainly an inflammatory factor secreted by CD4 T-cell (Th17), which can induce fibroblasts, keratinocytes, endothelial cells, epithelial cells, etc., to synthesize and secrete inflammatory factors such as G-CSF, IL-6, IL-8, MCP-1, PGE2, and is closely related to asthma, rheumatoid arthritis, lupus and other inflammatory diseases (Park et al., 2005).