American Association of Immunologists

Table I.

CD3⁺CD4⁺ Th and Treg cell populations: bona fide markers and function

Population	Defining Markers	Immune Target/Function	Alternative Molecules	References
Th1	CXCR3⁺CCR4⁻	Intracellular microbes	CD226, PD-1, T-bet	(3, 14, 15–17)
Th2	CCR4+CXCR3⁻	Extracellular parasites	GATA3	(3, 14)
Th17	CCR6⁺CD161+	Extracellular microbes/commensal	ICOS, RORC2	(2, 18–20)
Tfh	CXCR5⁺	B cell maturation	ICOS, PD-1, CD62L	(5, 21–23)
FOXP3 Treg	FOXP3⁺CD25^hiCD127^lo/−	Tolerance/immune suppression	TIGIT, CTLA-4, p-STAT5	(4, 7, 8, 24, 25)
Memory Tr1	CD45RA⁻LAG3⁺CD49b⁺	Peripheral Tolerance/myeloid killing	ICOS, PD-1, CD226	(4, 6, 26, 27)

Population	Defining Markers	Immune Target/Function	Alternative Molecules	References
Th1	CXCR3⁺CCR4⁻	Intracellular microbes	CD226, PD-1, T-bet	(3, 14, 15–17)
Th2	CCR4+CXCR3⁻	Extracellular parasites	GATA3	(3, 14)
Th17	CCR6⁺CD161+	Extracellular microbes/commensal	ICOS, RORC2	(2, 18–20)
Tfh	CXCR5⁺	B cell maturation	ICOS, PD-1, CD62L	(5, 21–23)
FOXP3 Treg	FOXP3⁺CD25^hiCD127^lo/−	Tolerance/immune suppression	TIGIT, CTLA-4, p-STAT5	(4, 7, 8, 24, 25)
Memory Tr1	CD45RA⁻LAG3⁺CD49b⁺	Peripheral Tolerance/myeloid killing	ICOS, PD-1, CD226	(4, 6, 26, 27)