ENTPD1 and rheumatoid arthritis: However, in RA patients, we observed a significantly higher percentage in cultures with IL-6, regardless of CD39 expression (p = 0.03 in CD39+ subset and p = 0.02 in CD39− subset) and CD73 expression (p = 0.05 in CD73+ subset and p = 0.03 in CD73− subset).