Construction of a cell model with membrane-surface expression of canine PD-1 and PD-L1 proteins in 293T cells by using eukaryotic expression systems.

Breakthrough progress has been made in the molecular mechanism research and clinical application of PD-1/PD-L1 in the regulation of immunosuppression and tolerance mainly in human and mouse fields, but is relatively slow in other species. The eukaryotic expression vectors pECFP-Fc-1 and pEYFP-Fc-L1 for high expression of canine PD-1 and PD-L1 proteins were constructed and transfected into human embryonic kidney 293 T cells. Fluorescence microscopy, laser scanning confocal microscopy, and immunofluorescence technology were used to identify the expression and membrane localization of the target proteins in human embryonic kidney 293 T cells. The binding activity of the target proteins expressed on the model cell was identified by eukaryotic expression vector co-transfection and immunocoprecipitation. The results showed that canine PD-1 and PD-L1 proteins were expressed on the membrane surfaces of their respective positively transfected cells. The cell membrane complex was further analyzed by co-immunoprecipitation technology, PD-L1 protein components were successfully detected in the pull-down complex of canine PD-1 antibody, and the two target proteins expressed in the model cells showed good mutual binding activity. Further research is needed to evaluate high throughput and a reliable method for screening drugs that block the PD-1 and PD-L1 pathway.