PDCD1 and neoplasm: In contrast with the previous findings, the effect of Bor on the expression of the PD-1 immune checkpoint receptor was not limited to the lymphocytes recruited to the tumor site, since the proportion of CD8+/PD-1+ cells was reduced both in the spleen and ascitic fluid, and that of CD4+/PD-1+ cells in the spleen of the drug-treated mice.