title: An automated particle counting immunoassay (PACIA) for determination of blocking antibodies against timothy grass pollen in sera from desensitized allergics.
abstract: An automated particle counting immunoassay (PACIA) for measurement of blocking antibodies (antigen neutralizing capacity) against timothy grass pollen extract in sera from desensitized allergics is described. Latex particles coated with F(ab')2-anti-timothy are agglutinated by timothy. Serum containing anti-timothy antibodies inhibits the agglutination. Non-agglutinated particles are counted in a modified AutoCounter. Nineteen of 20 sera from timothy allergics who had undergone immunotherapy with purified timothy extract for 30 weeks, showed significant agglutination-inhibition. None of 42 normal human sera gave significant inhibition. The inhibiting antibody could be removed by absorption with protein A and was thus of non-IgE nature, i.e. blocking antibody. The results obtained correlated statistically significantly with those found with a double-antibody method (rS = 0.62, n = 20, t = 3.35, P less than 0.01) and with the cumulated dosage of timothy allergen extract administered to the individual patient (rS = 0.56, n = 20, t = 2.87, P less than 0.02). Between-assay coefficient of variation was from 6.4% to 18.3%. The capacity is 40 samples per hour. The method has also been applied to measurement of blocking antibodies to honey bee and wasp venom.
mesh_terms: D000818:Animals; D000906:Antibodies / Q000032:analysis*; D000918:Antibody Specificity; D001322:Autoanalysis; D001667:Binding, Competitive; D006801:Humans; D007118:Immunoassay / Q000379:methods; D007167:Immunotherapy; D007840:Latex; D008863:Microspheres; D010316:Particle Size; D006109:Poaceae / Q000276:immunology; D011058:Pollen / Q000276:immunology*; D011817:Rabbits; D006255:Rhinitis, Allergic, Seasonal / Q000276:immunology* / Q000628:therapy
chemical_list: D000906:Antibodies; D007840:Latex