Human Extrafollicular CD4+ Th Cells Help Memory B Cells Produce Igs

• Published in: The Journal of immunology (1950) Vol. 201; no. 5; pp. 1359 - 1372
• Main Authors: Kim, Sang Taek, Choi, Jin-Young, Lainez, Begona, Schulz, Vincent P, Karas, David E, Baum, Eric D, Setlur, Jennifer, Gallagher, Patrick G, Craft, Joe
• Format: Journal Article
• Language: English
• Published: United States 01.09.2018
• Subjects: Adolescent; Antibody Formation; B-Lymphocytes - cytology; B-Lymphocytes - immunology; Child; Child, Preschool; Cytokines - immunology; Female; Gene Expression Regulation - immunology; Humans; Immunoglobulin G - immunology; Immunologic Memory; Male; Programmed Cell Death 1 Receptor - immunology; Proto-Oncogene Proteins c-bcl-6 - immunology; Receptors, CXCR5 - immunology; T-Lymphocytes, Helper-Inducer - cytology; T-Lymphocytes, Helper-Inducer - immunology
• ISSN: 0022-1767; 1550-6606; 1550-6606
• DOI: 10.4049/jimmunol.1701217

Follicular helper T (Tfh) cells are necessary for germinal center B cell maturation during primary immune responses; however, the T cells that promote humoral recall responses via memory B cells are less well defined. In this article, we characterize a human tonsillar CD4+ T cell subset with this function. These cells are similar to Tfh cells in terms of expression of the chemokine receptor CXCR5 and the inhibitory receptor PD-1, IL-21 secretion, and expression of the transcription factor BCL6; however, unlike Tfh cells that are located within the B cell follicle and germinal center, they reside at the border of the T cell zone and the B cell follicle in proximity to memory B cells, a position dictated by their unique chemokine receptor expression. They promote memory B cells to produce Abs via CD40L, IL-10, and IL-21. Our results reveal a unique extrafollicular CD4+ T cell subset in human tonsils, which specialize in promoting T cell–dependent humoral recall responses.