Serum levels of soluble programmed death-1 (sPD-1) and soluble programmed death ligand 1(sPD-L1) in systemic lupus erythematosus: Association with activity and severity.

The programmed cell death-1 (PD-1)/programmed cell death ligand 1 (PD-L1) pathway is an important host immunosuppression mechanism. Soluble PD-1 (sPD-1) and PD-L1 (sPD-L1) expression regulates co-inhibitory signals in autoimmune disorders. Here, we evaluated whether serum sPD-1 and sPD-L1 are involved in immune dysfunction and assessed its relationship with SLE. Blood samples were obtained from 130 patients with SLE and 44 healthy controls. Serum sPD-1 and sPD-L1 were tested by enzyme-linked immunosorbent assay (ELISA). Relevant immune parameters were analysed. Both serum sPD-1 and sPD-L1 were significantly higher in the SLE patients than in the controls. A series of severe disease clinical manifestations and laboratory features such as presence of decreased complement component 3, complement component 4 and SLEDAI >8 were associated with elevated sPD-1 and sPD-L1. Our study suggests that abnormal sPD-1 and sPD-L1 expression may be involved in the imbalance of immune regulation in SLE.