Additionally, the co-expression of CD3+ PD1+ was significantly higher in the control group (MFI = 19.02 ± 1.85) compared to severe SLE (MFI = 16.36 ± 1.83, p = 0.002) and mild SLE (MFI = 14.42 ± 2.43, p < 0.001) (Figure 5c). Here, PDCD1 is linked to systemic lupus erythematosus.