CD27 and rheumatoid arthritis: Flow cytometry analysis showed a higher percentage of memory (CD27+) versus naïve (CD27–) B cells in SF (CD27+ 73 ± 3.66% versus CD27– 29 ± 3.21%, p < 0.01) compared to PB (CD27+ 31 ± 3.89 versus CD27– 70 ± 3.91, p < 0.01) with no differences found between RA and PsA patients.