Figure 7.

(a) Results of an experiment to determine the fraction of the total IgG4 that reacts with grass pollen. Serum dilutions were incubated either with an anti-IgG reagent that will bind all IgG4 (open squares) or with Sepharose-coupled grass pollen extract (filled squares). Bound IgG4 is quantitated with iodinated anti-IgG4. The horizontal distance between the two dose–response curves indicates the potency ratio R = 0·26. Using the formula described in the Appendix, the conclusion is that c = 0·14, i.e. 14% of the IgG4 in this serum reacts with grass pollen. (b) Dilutions of the same serum are incubated either with Sepharose-coupled anti-IgG4 (open squares) or with Sepharose-coupled grass pollen extract (filled squares). Bound antibody is detected with affinity-purified radiolabelled mite allergen Der p1. The horizontal distance between the two dose–response curves indicates the potency ratio Q = 0·15, i.e. approximately 15% of the IgG4 that reacts with Der p1 reacts also with grass pollen. This is very close to the value of 14% predicted from the experiment shown in (a).