CD4 and pancreatic adenocarcinoma: Recent studies show that when gemcitabine is used for the treatment of locally advanced or metastatic pancreatic cancer, the number of naive CD4 T cells and resting memory CD4 T cells slightly increases, which reminds us that these two types of cells are upregulated in gemcitabine-resistant PAAD cells (Ullenhag et al., 2017).