Table 1.

The expression and function of DPP4 in immune cells.

	Expression	DPP4 Function	References
CD4+ T cells
Th1	High expression	Co-stimulation	(20)
Th2	Relative low expression	Elevated DPP4 expression was associated with the production of Th2 cytokines	(20, 21)
Th17	High expression	Co-stimulation, correlated with Th17 cytokine production	(22, 23)
Treg	Low expression		(24)
CD8+ T cells	High/negative expression	Co-stimulation	(25, 26)
B cells	Low expression	Co-stimulation, promote DNA synthesis, Ig production, and Ig isotype switching	(27, 28)
DCs	Positive expression	Modulate adenosine concentration by DPP4/ADA interaction, recruit Th1	(29, 30)
NK	Low expression	Co-stimulation, maintain cytotoxicity	(31, 32)
Macrophage	Positive expression	Regulatie M1/M2 macrophage polarization	(33, 34)
Fibroblast	Specific subpopulation	Activation marker	(16, 35)