PD-L1 blockade improves immune dysfunction of spleen dendritic cells and T-cells in zymosan-induced multiple organs dysfunction syndromes.

This research is to investigate the role of tolerant spleen dendritic cells (DC) in multiple organs dysfunction syndromes (MODS) at late stage. Tolerant DC and MODS were induced by intraperotineal injection of zymosan. The immunity of DC was determined by examining interleukin (IL)-10, IL-12, IL-2, major histocompatibility complex (MHC), CD86, programmed death (PD-1), programmed death ligand 1 (PD-L1), paired immunoglobulin-like receptor B (PIR-B) or T-cell proliferation in serum, spleen homogenate, DC culture or DC/T-cell co-culture. The PD-L1/PD-1 pathway was blocked using PD-L1 antibody. The IL-12p70 in serum, spleen homogenate and DC culture supernatant were decreased at 5 d and 12 d after zymosan injection while the IL-12p40 and IL-10 were increased. The expression of MHC, cluster of differentiation 86 (CD86), PD-1 and PD-L1 in spleen DCs were increased at early stage after zymosan injection. At 5 d and 12 d, the expression of MHC and CD86 was reduced while the expression of PD-1, PD-L1 and PIR-B was increased, accompanied with decreased proliferation of T-cell and decrease of IL-2 in spleen and serum. Application of PD-L1 antibody improved the above changes. At late stage of MODS mice induced by zymosan, the expression of co-stimulators and inhibitors in spleen DCs was imbalanced to form tolerant DCs which reduced the activation of T-cells. PD-L1 antibody improved the immune tolerance of DCs through intervening PD-1/PD-L1 pathway, and attenuated the inhibition of T-cell activities by tolerant DCs and the immune inhibition.