In vitro reaction of antibodies to ragweed. II. Quantitative determination of non-IgE antibodies interferring in a radioallergosorbent test.

Immunoglobulin E-rich fractions and IgE-depleted fractions were prepared from individual and pooled sera of patients allergic to ragweed. The IgE-depleted fractions contained antibodies to ragweed associated with the immunoglobulins G, A and M. The IgE-rich fraction contained only IgE antibodies to ragweed, although other immunoglobulins were present in this fraction. The amount of antibodies in these fractions was determined by the radioimmunoassay described in a preceding publication. The inhibitory role of the non-IgE antibodies was examined in an allergosorbent test (RAST) by using various concentrations of the IgE-rich fraction. The RAST was performed using ragweed-coupled cellulose powder as well as paper discs. The IgE antibodies in concentration from 0.017 to 0.069 mug/ml were inhibited by 30-60% in the cellulose RAST by non-IgE antibodies in concentrations from 6.25 to 12.5 mug/ml. The inhibition effect was substantially less pronounced in the paper disc RAST. This would indicate that for diagnostic purposes, especially for examination of sera with high levels of IgG antibodies, it is more reliable to use the disc RAST instead of the cellulose powder RAST.