HISTOCHERICAL CHARACTERIZATION OF PHA BINDING SITES IN CULTORED COEEIAC KUCOSA

Qualitative changes in lectin binding characteristics in coeliac disease have been previously described (Histochemistry 88,105,1988); in particular, the expression of PMA binding (Gal-GalMac residues) in goblet cells of coeliac mucosa appears to be an important point of histochemical difference between coeliac and control mucosae. In order to verify whether this PHA reactivity is modified in culture system, with and without the addition of a peptic-tryplic digest of A-gliadin (PI) at a concentration of 0.1 mg/ml, we have studied 4 cases of untreated coeliac mucosae placed in culture for 30 h in a serum-containing medium. All Bovin's solution-fixed paraffin-embedded sections were incubated with PHA-NRP conjugated lectin (Sigma Chemical Co.) as extensively elsewhere reported (Histochemistry 88, 105, 1988); prior to staining with PHA, parallel sections were digested with neuraminidase from Vibrio Cholerae (Calbiochem Corp.)(Lab Invest 47, 383, 1982). Adequate control procedures were also carried out. Flat intestinal mucosa from all coeliac patients underwent a clear morphological improvement when cultured for 30 h in the absence of PI and enterocyte height was considerably increased after culture. When the tissue culture was performed in the presence of PI, mo morphological or morphometric improvement was observed and necrotic areas and cell debris were found. An evident PNA reactivity was observed in the supranuclear region of enterocytes of regenerating mucosae and also in samples treated with PT;this PNA reactive pattern is unmodified by neuraminidase pretreatment. Inflammatory cells in the lamina propria are greatly stained after neuraminidase digestion. In uncultured samples of duodeno-jejunal biopsies from same patients, only goblet cells were reactive. Therefore we contend that untreated coeliac mucosae in culture system express new PHA binding sites as a consequence of quantitative changes in glycoproteins synthesis and secretion, as previously reported(6Ut 30,1339, 1989);t he unmodified PHA pattern after neuraminidase digestion may suggest an altered glycosilation in enterocytes since sialic acid groups are not incorporated or lacking in oligosaccharide chains.