For PD-1 expression, the co-expression of CD4+ PD1+ in lymphocytes had a significance between control (MFI = 144.56 ± 1.52) and severe SLE (MFI= 10.17 ± 1.66, p = 0.010) (Figure 6c). This evidence concerns the gene PDCD1 and systemic lupus erythematosus.