CR2 and rheumatoid arthritis: Moreover, naïve PsA showed similar IHC scores for CD21+ cells (0.75 ± 0.94) compared to naïve Abneg RA patients (0.52 ± 0.91; p = 0.43) (Fig. 1g), showing a direct correlation between ESR plasma levels and lining CD68+ cells IHC score (r = 0.66; p = 0.04).