This 37 kDa band likely corresponds to the procathepsin B3 based on its close approximation to the theoretical MW of 36.2 kDa deduced from the amino acid sequences of FgCatB3 (Meemon et al., 2004). In contrast, PoAb could detect a single band of 37 kDa in metacercairae and two bands of 37 and 34 kDa in NEJ WB extract which might reflect the existence of two isotypes in this antigen fraction (Fig. 2B, lane 5).