CD4 and cancer: In PDAC, cancer cells release tumor-associated antigens (TAAs) into the tumor immune microenvironment (TIME), where antigen-presenting cells (APCs) such as dendritic cells, macrophages, and antigen-presenting cancer-associated fibroblasts (apCAFs) internalize and present these antigens via major histocompatibility complex (MHC) class II molecules to CD4+ T-cells.