Figure 6. The competitive binding between various Igs or Ig/complement factors with schistosomal ligands.

(a) The competitive binding between IgG and IgM with seven proteins that bound to both types of immunoglobulins. The ELISA plates were coated with human IgG, and recombinant proteins were mixed with the same amount of human IgM by weight and then added to the wells. The OD₄₀₅ values were compared with those of wells without the addition of IgM (mean ± s.d. of three independent experiment replicates, *P < 0.05, **P < 0.01, n.s., not significant, two-tailed Student’s t-test). (b) Comparison of the binding of C1qBP with human C1q and IgG by ELISA. Plates were coated with equal amounts of human IgG and C1q by weight and incubated with doubling diluted recombinant C1qBP. C1qBP bound to both human IgG and C1q, and the OD values for the binding to human IgG were even higher than those for C1q. (c) The inhibitory effect of human IgG on the binding between complement and C1qBP was investigated using an ELISA assay. ELISA plates were coated with C1q prior to incubation with C1qBP mixed with human IgG at various concentrations (mean ± s.d. of three independent experiment replicates, *P < 0.05, **P < 0.01, ***P < 0.001, n.s., not significant, two-tailed Student’s t-test). IgG significantly competed with the binding of C1q to C1qBP.