SOME CHARACTERISTICS OF IMMUNOFLUORESCENCE TESTS FOR ANTIBODIES AGAINST GLUTEN, USING WHEAT GRAIN SECTIONS OR GLIADIN COATED SEPHAROSE BEADS

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Abstract
Human antibodies against gluten and gliadin were determined by the indirect immunofluorescence technique, using frozen wheat grain sections or gliadin-coated Sepharose beads. Methodological characteristics and diagnostic usefulness of the 2 techniques were evaluated. The reproducibility of both was improved by introducing a fluorometric reading-off procedure. Antibody quantitations were preferably performed as end-point titrations. The 2 techniques had different dose-response relationships. The grain section technique was more discriminative for small variations in antibody concentration than the bead technique. The latter was more reproducible. Besides antibodies against gliadin, a number of patients with gluten enteropathy had antibodies against the main septa of wheat grains. Fluorescence intensity was preferably expressed in multiples of background intensity. A reaction was visually perceived when the fluorometrically-measured fluorescence intensity reached 2.5 times the background intensity. Using this value as the limit for positive reactions, antibodies were demonstrated in 81% of the cases with verified gluten intolerance, compared with 28% in cases with other intestinal allergies and 8% in normals. The diagnostic specificity of both the grain section and Sepharose bead technique for gluten enteropathy increased with increasing antibody concentration and was apparently 100% when the fluorescence intensity produced by a 1/10 serum dilution reached a value 7-8 times that of the background. Antibodies against reticulin were demon in 1/4 of the cases having anti-gluten antibodies but in none of those with non-gluten-induced gastrointestinal symptoms. Antibodies of the IgG class against cow''s milk were demonstrated more often and in higher titer in cases with anti-gluten antibodies than in those without them.