Table 1.

The functions of MSCs in regulating different immune cells and the related mechanisms

Immune cell type	MSC function	Mechanism	References
T cell	Suppressing T cell differentiation, proliferation, activation, and survival	TGF-β, HGF, IDO, NO, PGE2, HLA-G5, TSG6, IL-10, EVs	[30, 31, 34, 35, 43, 62–66, 69–71, 180]
		Cell–cell contact: Fas/FasL signaling	[33]
	Promoting T cell recruitment	CXCR3 ligands, CCR5 ligands, ICAM-1, VCAM-1	[17, 43, 44, 46]
B cell	Suppressing B cell differentiation, proliferation, activation, and chemotaxis; Breg induction	CCL2, IL-1Ra, IDO, PGE2, complement C3, EVs	[60, 78, 81–84, 87, 90, 180]
		Cell–cell contact: PD-1/PD-L1	[85]
	Promoting B cell differentiation, proliferation, and activation	VEGF	[93, 94]
DC	Suppressing DC differentiation, activation, endocytosis, migration, and maturation	IL-6, IL-10, M-CSF, PGE2, EVs	[36, 65, 99, 101–103, 107–109, 113, 114]
		Cell–cell contact: notch pathway activation	[100]
Macrophage	Suppressing M1 while inducing M2 polarization	PGE2, IDO, IL-1Ra, IL-10, TSG-6, TGF-β, exosomes	[68, 83, 123, 125, 126, 131, 135, 136]
NK cell	Suppressing NK cell proliferation, migration, and activation	IDO, PGE2, HLA5, EVs	[35, 60, 142–147]
		Cell–cell contact: CD73, TLR4	[147, 149–151]
	Promoting NK cell progenitor proliferation and NK activation	CCL2	[152–154]
Neutrophil	Suppressing neutrophil activation, recruitment, neutrophil extracellular trap formation, and protease secretion	Superoxide dismutase-3, EVs	[166–168]
	Promoting survival and recruitment	IL-6, IL-8, MIF, IFN-β, and GM-CSF	[159–162]
Mast cell	Suppressing mast cell degranulation, inflammatory cytokine secretion, and chemotaxis	PGE2 and TGF-β1	[172–177]