CD8A and rheumatoid arthritis: The mean percentages of CD3+CD8+CD28null T cells out of CD3+CD8+ T cells were 38.4 ± 21.9% in AS, 44.4 ± 21.7% in PsA and 46 ± 26.2% in RA, compared with 22.3 ± 12.4% in the control group (each with P < 0.001, Figure 1b).