CD19 and rheumatoid arthritis: As in synovial tissues, significantly a higher level of OX40L expression was detected in the monocytes (Figure 1G), DCs (Figure 1H), and B cells (Figure 1I) of RA patients relative to OA patients, and RA patients also exhibited a higher frequency of circulating CD11c+ DCs (Figure 1J), CD19+ B cells (Figure 1K), and CD14+ monocytes (Figure 1L) as compared to OA patients.