The expression of HLA class II genes, the major ligand in the MHC-II pathway, was significantly downregulated in classic monocytes in RA, and there was a relationship between this class of genes and inflammatory factors such as TNF and IL1B, and chemokines such as CCL3 and CCL3L1, and chemokines such as CCL3 and CCL3L1. The gene discussed is CCL3; the disease is rheumatoid arthritis.