Variable Increased Expression of Program Death-1 and Program Death-1 Ligands on Peripheral Mononuclear Cells Is Not Impaired in Patients with Systemic Lupus Erythematosus

Programmed death-1 (PD-1) was shown to deliver an inhibitory signal after binding to its ligands, PD-L1 (B7-H1) or PD-L2 (B7-DC). Recently, up-regulated expression of PD-1 molecule and/or its ligands was demonstrated in human diseases including rheumatoid arthritis and inflammatory colitis. The study aimed to investigate the expression and function of PD-1 and PD-1 ligands on circulating T cells, B cells and monocytes from patient with systemic lupus erythematosus (SLE). The results showed that patients with SLE had significantly increased percentages of PD-1-expressing CD3(+)T cells and CD19(+)B cells, PD-L1-expressing CD19(+)B cells and PD-L2-expressing CD14(+)B monocytes. In selected SLE patients and normal subjects, functional study of PD-1/ PD-1 ligands pathway on the production of cytokines by stimulated PBMC was examined. Blockages of PD-1 or PD-1 ligands substantially increased the production of IL-2, IFN-γ and IL-10, the amplitude of increase roughly ranged from one to three times. There were no significant differences of the enhancing effects on cytokine production by blockage of PD-1/PDL pathway between SLE patients and normal subjects. The study indicates that there are no intrinsically defective expression and function of PD-1 and PD-1 ligands on PBMC in patients with SLE.