CD40LG and infection: To further validate the function of Tfh in B cells during S. japonicum infection in FVB mice, we sorted Tfh cells and B cells from spleen tissue at different infection stages, and our co-culture experiment data showed that blockading IL-21 with IL-21R blocking mAb, the production of IgM in cell supernatant was lower than that the control group (Fig. 4d).