To identify the earliest evidence of class-switching in the humoral response to worm antigens during pre-patent infection, ELISAs using plate-bound soluble worm antigen (SWAP) were used to detect SWAP-specific IgM, IgG1 and IgG2b in plasma of infected mice at 0, 1, 2, 3, 4 and 8 weeks post infection (Figure 1 A-C). Here, CD40LG is linked to infection.