Some characteristics of immunofluorescence tests for antibodies against gluten, using wheat grain sections or gliadin coated sepharose beads.

Antibodies against gluten and gliadin were determined by the indirect immunofluorescence technique, using frozen wheat grain sections or gliadin-coated Sepharose beads. The methodological characteristics and diagnostic usefulness of the two 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 two 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, however, 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 to 8 times that of the background. Antibodies against reticulin were demonstrated in 1/4 of the cases having anti-gluten antibodies but in none of those with non-gluten-induced gastro-intestinal symptoms. Antibodies of the IgG class against cow's milk were demonstrated more often and in higher titre in cases with anti-gluten antibodies than in those without them.