PD-1 (CD279) expression percentages on CD4+ T cells was significantly greater on RA patients’ CD4+ T cells instead of on those from healthy volunteers, as shown in Table 1 (4.6 (9.625), (N = 48) vs. 3.1 (6.9), (N = 27), p = 0.0088). Here, PDCD1 is linked to rheumatoid arthritis.