Bossaller L, Burger J, Draeger R, Grimbacher B, Knoth R, Plebani A, Durandy A, Baumann U, Schlesier M, Welcher AA, Peter HH, Warnatz K

Bossaller L, Burger J, Draeger R, Grimbacher B, Knoth R, Plebani A, Durandy A, Baumann U, Schlesier M, Welcher AA, Peter HH, Warnatz K. by memory B cells upon seasonal influenza vaccination. INTRODUCTION Influenza vaccines provide protection mainly by generating high-affinity antibodies against hemagglutinin, thereby preventing virus entry (1, 2). Immunological events that GSK2200150A lead to the development of protective immunity GSK2200150A after vaccinations remain largely unknown. Antibody response requires CD4+ helper T (TH) cells, most particularly a TH subset, T follicular helper (TFH) cells (3, 4). TFH cells are essential for the generation of high-affinity memory B cells through the germinal center (GC) reaction (3C5). TFH cells express the chemokine (C-X-C) receptor 5 (CXCR5) (6C9), which guides their migration into B cell follicles. Inducible costimulator (ICOS), expressed at high density by TFH cells in human tonsils (9), plays a critical role for their development (10C12) and functions (13, 14). TFH cells support the differentiation and survival of GC B cells (15, 16) through the secretion of interleukin-21 (IL-21) (17, 18). Tonsillar TFH cells express the transcription repressor B cell lymphoma 6 (Bcl-6) (9, 18C20), which is essential for TFH cell generation in vivo (21C23). In addition to GC response, CD4+ T cells also provide help to B cells at extrafollicular sites and induce their differentiation into plasma cells that contribute to the early generation of specific antibodies after antigen challenge (24). Extrafollicular helper cells appear to share developmental mechanisms, phenotypes, and functional properties with TFH cells (18, 25C27). CXCR5+CD4+ T cells are also found in human blood and share functional properties with TFH cells (28, 29). This is also supported by the observations that subjects who show severely impaired GC formation through deficiency of CD40 ligand or ICOS display substantially fewer circulating CXCR5+CD4+ T cells (11). We have previously shown that human blood CXCR5+CD4+ T cells are composed of subsets that differentially express the chemokine receptors CXCR3 and CCR6, and display different functions (28). For example, CXCR3+CCR6? cells produce interferon- (IFN-), whereas the CXCR3?CCR6+ cells produce IL-17A (28). At variance with TFH cells in secondary lymphoid organs, blood CXCR5+CD4+ T cells are in a resting state and do not express ICOS (28, 29). In patients with clinically active autoimmune diseases, such as systemic lupus erythematosus, blood CXCR5+CD4+ T cells express ICOS (30), suggesting that they are activated. Here, we hypothesized that the detailed phenotypical analysis on blood CXCR5+CD4+ T cells and their subsets might provide insights regarding the mechanistics by which influenza vaccinations induce protective antibody responses. Here, we show evidence that ICOS+CXCR3+CXCR5+CD4+ T cells emerging in blood 7 days after influenza vaccination contribute to the development of antibody responses by providing help to memory B cells. RESULTS Influenza vaccination induces ICOS on CXCR3+CXCR5+CD4+ T cells Initially, two cohorts of healthy subjects were accrued in this study. A nonadjuvanted trivalent split seasonal influenza vaccine (Fluzone) was administered to a cohort of healthy adults (= 12, called adult cohort) during winter 2009/2010 and to a cohort of healthy children (= 19, called children cohort) during winter GSK2200150A 2010/2011. The CDC7 two vaccines shared the influenza B strain (B/Brisbane/60/2008-like). The influenza H3N2 strains were different [2009/2010: A/Brisbane/10/2007 (H3N2)Clike; 2010/2011: A/Perth/16/2009 (H3N2)Clike] but largely similar (for example, the identity of hemagglutinin sequences was 98%). However, only the 2010/2011 vaccine contained a component derived from swine-origin H1N1 influenza strain [A/California/7/2009 (H1N1)Clike], a pandemic strain in the year 2009 to 2010 (31); the 2009/2010 vaccine contained A/Brisbane/59/2007 (H1N1)Clike strain. The percentage of total CD4+ T cells as well as CXCR5+CD4+ T cells in blood did not change at any time points after vaccination (days 1, 3, 7, 10, 14, 21, and 28) (fig. S1; the gating strategy is shown in Fig. 1A). However, the frequency of CD4+ T cells expressing ICOS GSK2200150A increased after vaccination and GSK2200150A peaked on day 7 (Fig. 1B). The up-regulation of ICOS was largely confined to CXCR5+CD4+ T cells because the frequency of ICOS+ cells within the memory CXCR5?CD4+.