CD40LG and pertussis: B cells producing IgM against pertussis increased significantly between HC and PERTUSSIS mothers (PT and PRN p ≤ 0.0001; FHA p = 0.0002), but, in contrast to switched memory B cells, IgM memory B cells able to bind pertussis antigens also increased significantly in mothers of children with LRTI (PT p = 0.002; FHA p = 0.004; PRN p = 0.03) (Figure 3C).