Materials and Methods: The frequency and phenotype, including CCR1 and CCR2, of the PBMC populations (monocytes, CD19+B cells, and T/NK lymphocytes) in RA (n = 15) and OA (n = 10) patients and HC (n = 12) were analyzed by five-color flow cytometry. This evidence concerns the gene CCR2 and rheumatoid arthritis.