. Author manuscript; available in PMC: 2022 Aug 1.

Published in final edited form as: Trends Immunol. 2021 Jul 6;42(8):658–669. doi: 10.1016/j.it.2021.06.003

Table 1: A proposal of three groups of Tfh and Tfh-like subsets based on anatomical location of function.

BCL6-dependent indicates that Bcl6/BCL6 is required for development, even if it is no longer highly expressed. Secondary lymphoid organs (SLO) include lymph nodes, spleen, Peyer’s Patches, etc. cTfh, circulating Tfh; EF, extrafollicular; GC, germinal center; NKTfh, Natural killer Tfh; Tfh, T follicular helper; Tfr, T follicular regulatory; Th, T helper; Tph, T peripheral helper; Trh, T resident helper; PB, peripheral blood; CSR, class switch recombination. Grey text indicates the cell subsets that have not been well defined.

Site	Tfh & Tfh-like cell subsets	BCL6-dependent	Group 1	Group 2	Group 3	Primary Function
Secondary Lymphoid Organs	Tfh	YES	Tfh1	Tfh2	Tfh17	Priming, differentiation & CSR of antigen-stimulated B cells
	GC-Tfh	YES	GC-Tfh1	GC-Tfh2	GC-Tfh17	GC B cell selection
	SLO-Th	NO	SLO-Th1	SLO-Th2	SLO-Th17	Priming, differentiation & CSR of antigen-stimulated B cells
	EF-Tfh	?	EF-Tfh1	EF-Tfh2	EF-Tfh17	PB expansion in chronic inflammatory conditions
	NKTfh	YES	NKTfh1	NKTfh2	NKTfh17	Boost B cell priming
	Tfr	YES	Tfr1	Tfr2	Tfr17	Tfh regulation, GC B cell selection
Blood	cTfh	YES	cTfh1	cTfh2	cTfh17	Circulating memory reservoir
Non-lymphoid Tissues	Tph	?	Tph1	Tph2	Tph17	In situ B cell activation
Non-lymphoid Tissues	Trh	YES	Trh1	Trh2	Trh17	Reactivation of memory B cells in situ