CTLA4 and familial pancreatic carcinoma: Dendritic cells were chosen for the experiments to obtain representative numbers of cellular events with positive or negative CTLA4 expression but also because dendritic cells are obtained by stimulating PBMC with GM-CSF, a cytokine recently demonstrated to be highly expressed by pancreatic cancer and necessary and sufficient for in vitro generation of functional immunosuppressive Gr-1+CD11b+ cells in mice [26].