CD274 and parasitic infectious disease: In parasitic infections, PD-1/PD-L1 or PD-1/PD-L2 signaling has been reported to be involved in the immune responses to protozoa, nematode, trematode, and cestode infections [32]; however, the effect of a C. hepatica infection on the regulation of the PD-1/PD-L1 or PD-L2 signaling pattern has not been previously reported.