Ultrastructural localization of concanavalin a surface receptors on brush-border enterocytes in normal children and during coeliac disease.

Concanavalin A surface receptors were detected on brush border enterocytes from child intestinal biopsies by the concanavalin A-peroxidase method. On electron microscopy, these receptors appeared as electron-dense deposits, located on a band running along the innermost part of the brush border membrane glycocalyx. In the five control subjects tested, brush border length was 1.06 +/- 0.18 micrometer, and band thickness, 19 +/- 4 nm. Deposits were regular in shape and evenly spaced out along the entire membrane, reflecting homogeneous glycosylation of the normal brush border. In seven patients with villous atrophy induced by gluten, the brush border was damaged and its length was 1.04 +/- 0.39 micrometer. The thickness of the electron-dense deposit band was 19 +/- 6 nm; deposit shape was irregular and the band ran discontinuously along the membrane. The degree of this abnormality seemed to correspond to the degree of brush border damage. In six treated coeliac patients with normalized mucosa, the brush border was structurally normal but it was significantly longer (1.25 +/- 0.32 micrometer) than in the controls (p less than 0.01). The electron-dense band was significantly thinner (16 +/- 7 nm) than in the controls (p less than 0.01). The distribution of the electron-dense deposits was sporadic in some parts of the band and regular in others. These results suggest abnormal glycosylation of the brush border membrane in coeliac disease, and might be due to the presence of abnormal glycoconjugates. It remains to be established if these changes are induced by gluten toxicity or are the consequences of nonspecific intestinal disorders.