title: Loss of IL-7 receptor alpha on CD4+ T cells defines terminally differentiated B cell-helping effector T cells in a B cell-rich lymphoid tissue.
abstract: IL-7 plays important roles in development and homeostatic proliferation of lymphocytes. IL-7 uses a receptor composed of IL-7Ralpha (CD127) and the common gamma-chain (CD132) to transmit its signal. It has been unknown how CD127 is regulated during Th cell differentiation to the B cell-helping T cell lineage. In this study, we report that loss of CD127 defines terminally differentiated B cell-helping effector T cells in human tonsils. Although naive CD4(+) T cells uniformly express CD127, the memory/effector (non-FOXP3(+)) CD4(+) T cells are divided into CD127(+) and CD127(-) cells. The CD127(-) T cells are exclusively localized within the germinal centers where B cells become plasma and memory B cells, whereas CD127(+) T cells are found in T cell areas and the area surrounding B cell follicles. Consistently, the CD127(-) T cells highly express the B cell zone homing receptor CXCR5 with concomitant loss of CCR7. Compared with CD127(+) memory T cells, CD127(-) T cells have considerably shorter telomeres, do not proliferate in response to IL-7, and are prone to cell death. The CD127(-) T cells produce a large amount of the B cell follicle-forming chemokine CXCL13 upon stimulation with B cells and Ags. Most importantly, they are highly efficient in helping B cells produce Igs of all isotypes in a manner dependent on CD40L and ICOS and inducing activation-induced cytidine deaminase and Ig class switch recombination. The selective loss of CD127 on the B cell-helping effector T cells would have implications in regulation and termination of Ig responses.
authors.affiliation: Laboratory of Immunology and Hematopoiesis, Department of Comparative Pathobiology, Purdue Cancer Center, Purdue University, West Lafayette, IN 47907, USA.
authors.forename: Hyung W
authors.initials: HW
authors.lastname: Lim
authors.forename: Chang H
authors.initials: CH
authors.lastname: Kim
mesh_terms: D000293:Adolescent; D001402:B-Lymphocytes / Q000276:immunology*; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D002454:Cell Differentiation / Q000276:immunology*; D016207:Cytokines / Q000276:immunology; D051858:Forkhead Transcription Factors / Q000378:metabolism; D006801:Humans; D016130:Immunophenotyping; D014066:Palatine Tonsil / Q000276:immunology*; D054400:Receptors, CCR7 / Q000096:biosynthesis; D054380:Receptors, CXCR5 / Q000096:biosynthesis; D020395:Receptors, Interleukin-7 / Q000502:physiology*; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology*
chemical_list: C515370:CCR7 protein, human; C095085:CXCR5 protein, human; D016207:Cytokines; C418974:FOXP3 protein, human; D051858:Forkhead Transcription Factors; D054400:Receptors, CCR7; D054380:Receptors, CXCR5; D020395:Receptors, Interleukin-7; C415350:interleukin-7 receptor, alpha chain