PDCD1 and neoplasm: Thus, and as reported in the tumor microenvironment (TME) of distinct human cancers [21,28,29,50,57], positive correlations were observed between serum VISTA levels and several immune inhibitory checkpoint proteins [58], such as serum PD-1 (p < 0.0001), PD-L1 (p < 0.0001), CTLA-4 (p < 0.0001), and LAG-3 (p = 0.0002), as well as with the cytokines IL-6 (p = 0.0016) and TNF-α (p < 0.0001), proposing not only a co-regulation among these molecules [20,55,59,60] but also an immunosuppressive status of these animals, reinforcing previously reported data [19,22].