sPD-L1 Expression is Associated with Immunosuppression and Infectious Complications in Patients with Acute Pancreatitis

Acute pancreatitis (AP) with infectious complications has high mortality because of early-stage immunosuppression. The programmed cell death-1 (PD-1)/programmed cell death ligand 1 (PD-L1) pathway is an important host immunosuppression mechanism. Soluble PD-L1 (sPD-L1) expression regulates co-inhibitory signals in malignancies or autoimmune disorders; however, its effects in AP are unknown. Here, we evaluated whether serum sPD-L1 is involved in immune dysfunction and assessed its relationship with infectious complications in early AP. Blood samples were obtained from 56 patients with acute pancreatitis and 21 healthy individuals in this prospective study. Serum sPD-L1 levels within 48 h after AP onset were tested by enzyme-linked immunosorbent assays. Relevant immune parameters (human leucocyte antigen-DR, lymphocyte count) and inflammatory markers (C-reactive protein, white blood cell count) were analysed. sPD-L1 was significantly upregulated in patients with early AP, especially those with infectious complications, compared to healthy controls. Significant negative correlations were observed among monocyte HLA-DR expression, lymphocyte count and sPD-L1 levels in AP. Multivariate regression indicated that sPD-L1 was an independent risk factor for infectious complications in AP. The findings suggest that increased sPD-L1 expression appears to be involved in the development of immunosuppression in the early stage of AP and that sPD-L1 might be an early parameter for prediction of infectious complications in patients with AP.