Help from specific CD4+ subsets of T cells to B cells is a prerequisite for this humoral immunity. Follicular T helper (TfH) cells are a newly recognized lineage of CD4+ T cells [11], that were

originally discovered in the B cell follicles of secondary lymphoid organs with the defining feature of high expression of the chemokine receptor CXCR5. There are accumulating evidences that these TfH cells are the key T-cell subset required for the formation of germinal centers (GCs) and the generation of antigen specific T cell-dependent antibody responses [11], [12], [13], [14] and [15]. That TfH cells are actively engaged in responses find more to vaccination has been shown in a number of different virus systems. Bentebibel et al. reported that peripheral TfH-like cells, marked as CD4+ICOS+CXCR3+CXCR5+, are associated with protective antibody responses after seasonal flu vaccination [16]. The efficacy of the foot and mouth disease vaccine (FMDV) may also be enhanced through the generation

of TfH cells [17] and [18]. Furthermore, the non-responsiveness of HIV-infected individuals to the 2009 H1N1 vaccine has been primarily attributed to the impairment of circulating TfH cells [19]. In the case of HBV, the abnormal expressions of TfH-related molecules have been reported to be at least Selleck UMI-77 partially responsible for the dysfunction of immune responses during chronic HBV infection [20] and [21]. Despite this clear evidence that TfH cells have an important role

in the humoral immune response to a number of vaccines, the relationship between TfH cells and specific antibody responses to HBV vaccine has not as yet received sufficient attention. Given the growing recognition of the importance of TfH cells in generating a strong humoral immune response, it seems reasonable to hypothesize that polymorphisms of TfH related molecules may be associated with non-responsiveness to HBV vaccination. Therefore, in this study a total of 24 single nucleotide polymorphisms (SNPs) within six genes (CXCR5, ICOS, CXCL13, IL-21, BCL6 and CD40L) were selected and analyzed. The cohort recruited for the current study was a subset from a previous survey unless on non-responders to HBV vaccine [4] and [22]. The details for screening were described in Supplementary Fig. 1. In brief, a total of 37,221 ethnic Han Chinese volunteers with no hepatitis B vaccination history were recruited. All recruited volunteers were vaccinated with 10 μg of recombinant HBV vaccine (Shenzhen Kangtai Biological Products Co., Ltd., Shenzhen, Guangdong) according to the standard 0, 1, and 6 months vaccination schedule. Anti-HBs titers were tested at 7th month after initiating the vaccination regime and individuals whose anti-HBs titer was lower than 10 mIU/ml were re-vaccinated with a further 3 doses of HBV. Levels of Anti-HBs antibody were re-tested approximately one month after the final dose of vaccine was administered.