Figure 2.

Effector immune cells and immunosuppressive cells in human pancreatic cancer. Activated CD8⁺ T cells attack tumor cells presenting tumor-associated antigens peptides on their surface, as dendritic cells. CD4⁺ T cells target tumor cells either directly by eliminating tumor cells through cytolytic mechanisms or indirectly by modulating the TME. Tregs and MDSCs cells play immunosuppressive roles in inhibiting the immune response against PDAC cells by directly inhibiting the anti-tumor functions of T and NK cells. The TAM phenotype is a consequence of the continuous presence of growth factors such as colony-stimulating factor-1 (CSF1) and its receptor (CSF-1R). TAMs release various growth factors and cytokines and promote tumor cell invasion, induce angiogenesis, suppress antitumor immunity, and facilitate tumor cell metastasis. CSF-1R: colony-stimulating factor-1 receptor; MDSC: myeloid-derived suppressor cells; NK: natural killer; TAMs = tumor-associated macrophages; Treg = regulatory T cell.