CD4 and pancreatic adenocarcinoma: The number of cytotoxic CD8+ T cells [5, 6], which execute surveillance and elimination of tumour cells, predicted a better prognosis of PAAD patients, while the CD4+ T-lymphocytes were prone to exhibit a tumour-promoting effect on PAAD by the secretion of a series of oncogenic cytokines that can primarily affect the capacity of cytotoxic T lymphocytes (CTLs) [7–11].