The violin plot (Fig. 6B) indicated that the proportions of B cells memory (P = 0.005), T cells regulatory (Tregs) (P = 0.003) and NK cells activated (P < 0.001) were relatively high in OA synovial tissues compared with that in RA synovial tissues, while B cells naive (P < 0.001), plasma cells (P = 0.004), T cells CD4 naive (P = 0.018), T cells CD4 memory activated (P = 0.001), dendritic cells activated (P = 0.003) and eosinophils (P < 0.001) were relatively low in OA. Here, CD4 is linked to rheumatoid arthritis.