In vitro co-culture of Tfh cells or Tfh depleted T helper cells with B cells after 7 days, with antigenic stimulation (MP, mCT, or SEB) and a media only control (n=11). Data are presented as the mean concentration of IgG in ng/ml of culture supernatant, with error bars representing the standard errors of the mean. B, Tfh+ and Tfh- cells are defined as CD19+ cells, CD3+CD4+CD45R0+CXCR5+ cells and CD3+CD4+CD45R0+CXCR5- cells, respectively. An asterisk represents a significant decrease of IgG after depletion of Tfh compared to nondepleted Tfh cells (* <0.05, **<0.01).