For instance, the combination of programmed death receptor-ligand 1(PD-L1) expressed by tumor cells and PD-1 expressed by CD8+ toxic T cells can promote the inactivation or apoptosis of CD8+ toxic T cells, thus weakening the host's antitumor immune response.[39] CD8+ toxic T cells are cytotoxic lymphocytes that damage targeted cells via the production of enzymes such as granzyme-B and perforin.[38] Our results imply that FOXP4-AS1 has a strong negative correlation with the infiltration of cytotoxic cells. The gene discussed is PRF1; the disease is neoplasm.