In veterinary virology or cancer research, there are a few reports on the PD-1 and PD-L1 homologs in cats, pigs and bovines, however their interactions and potential applications for immunotherapy have not been studied in detail (Jeon et al., 2007; Ikebuchi et al., 2011; Maekawa et al., 2014; Zhu et al., 2017). This evidence concerns the gene PDCD1 and cancer.