Table 2.

Summary of immune cells in the tumor microenvironment of pancreatic adenocarcinoma.

Immune Cell Type	Infiltration and distribution			Related Cytokines	Function	Prognostic factors associated with PDAC	Other known immune functions
	Pancreatitis	Pancreatic ductal intraepithelial neoplasia	PDAC
Neutrophil	High	Present	Very low	IL-8, C5a, MMP	Promoting inflammation, promoting cancer	No difference in various types of PDAC	Resist pathogens such as bacteria and viruses.
TAM
M1	High	Present	Present	IFN-γ, IL-12, IL-23, TNF-α	Promoting inflammation, promoting cancer		Participate in th1 type immune response, killing pathogens and tumor cells
M2	Low	Low	High	IL-4, IL-10, IL-13, TGF-β	Immunosuppression	Poor survival rate	Mediates Th2-type immune response and plays a major role
MDSC	Present	Low	High	GM-CSF, VEGF, TGF-β	Immunosuppression, decreased CD8 + T cell infiltration	Poor survival rate	Suppress immune cell response
T cell
Treg	Present	Low	High	TGF-β, IL-6	Immunosuppression, decreased CD8 + T cell infiltration	Poor survival rate	Immunosuppression and tolerance.
Helper T cell
Th1	Present	Low	Low	IL-2, IFN-γ	Immune activation	Better survival rate	Assist in the removal of microorganisms in cells
Th2	Present	Low	High	IL-4, IL-5, IL-6, IL-13	Immunosuppression	Poor survival rate	Participate in allergic reactions against
Effector T cell	Present	Low	Low	IFN-γ, TNF-α, IL-2	Antitumor immunity	Better survival rate	Recognize infected cells and bind to cell
Th17 cell				IL-17A,IL-17F,IL22,TNF-α	Promoting inflammation		Activate neutrophils, mediate inflammation, and tumor immunity.
DCs				L12,IL18,cck	Antitumor immunity		Inducing specific CTL anti-tumor immune response.

TAM, tumor-associated macrophage; VEGF, vascular endothelial growth factor; MDSC, myeloid-derived suppressor cell.