Identification of anti-idiotypic antibodies in the sera of ryegrass-allergic and nonallergic individuals

Anti-idiotypic (Id) antibodies (Abs) are generated in the humoral response to antigen (Ag). Some of these anti-Id Abs are capable of binding to the combining site or paratope of Abs that bind Ag. These Ab2 can competitively inhibit the binding of Ab1 to Ag and may trigger an Ab1 response similar to the response induced by Ag. To determine if specific Ab2 that inhibit the binding of IgE Abs to ryegrass (RG)-pollen allergens are present in the sera of RG-allergic (RGA) individuals before the initiation of allergen-specific hyposensitization with RG-pollen extract, we studied sera from five RGA and four nonallergic (NA) subjects in an IgE anti-RG RAST-inhibition assay. Ab2-enriched serum fractions were prepared from these study subjects by exhaustive mixed grass-pollen affinity chromatography to remove IgE and IgG anti-RG Ab1 from whole serum aliquots containing Ab1. Unabsorbed, twice-concentrated sera were diluted to one-time concentrated sera with equal volumes of either Ab2-enriched sera without Ab1 or borate-buffered saline absorbed by mixed grass-pollen affinity chromatography. IgE anti-RG Ab1 was determined by a standard RG RAST assay. We have detected Ab2 in the sera of the RGA patients, which inhibit the binding of autologous and allogeneic IgE anti-RG to RG Ags in solid phase. Parallel RG RAST assays with sera from NA subjects demonstrated no significant inhibition. Ab2-enriched sera from some grass-allergic and some NA subjects inhibited IgE anti-RG binding found in some RGA patients' sera. We conclude that anti-Id Abs, Ab2, specific for IgE anti-RG, Ab1, are present in some RGA patients and NA individuals.