Antibody responses to deamidated gliadin peptide show high specificity and parallel antibodies to tissue transglutaminase in developing coeliac disease

Coeliac disease (CD) is an enteropathy induced in genetically susceptible individuals by gluten components, gliadin, hordein and secalin, polypeptides present in cereals such as wheat, barley and rye, respectively. Although the disease starts as intolerance to gliadins, antibodies to tissue transglutaminase (tTG) in the gut epithelium are characteristic of the disease. Whereas serum autoantibodies against tTG (tTGA) are highly specific for CD, antibodies to gliadin are less informative as they can also be detected in other enteropathies, and even in healthy individuals. However, it was shown recently that antibodies to certain gliadin peptides occur with high specificity in CD patient sera. We developed a solid phase lanthanide-based immunofluorometric assay for simultaneous detection of serum IgA and IgG antibodies to a synthetic peptide derived from gamma gliadin of wheat comprising amino acids 86-103. Three glutamine residues of this native 18-mer peptide were replaced by glutamic acids and the peptide was biotinylated. Sera from 87 individuals who had undergone duodenal biopsy and were diagnosed with CD and from 81 healthy individuals were analysed for the presence of both IgA and IgG anti-gliadin peptide antibodies. The performance of the peptide AGA assay was excellent, showing a specificity and sensitivity of 90% and 92% for IgA, and 98% and 75% for IgG, respectively. The corresponding values for conventional anti-gliadin antibody (AGA) enzyme-linked immunosorbent assay (ELISA) tests were 72% specificity and 87% sensitivity for IgA, and 64% specificity and 78% sensitivity for IgG. In a prospective study, almost all the tTGA-positive sera drawn from children who later developed CD were also positive for gliadin peptide antibodies.

Serum IgA anti-gliadin antibodies in an adult population sample. High prevalence without celiac disease

IgA-class anti-gliadin antibodies (AGA) and IgA-, IgG-, IgM-class anti-reticulin antibodies (ARA) were determined in 1461 persons, representing 84% of a population from the village of Karksi-Nuia. AGA were detected by enzyme-linked immunosorbent assay (ELISA) and ARA by indirect immunofluorescence. Fifty-two (3.5%) persons had IgA-class AGA, of whom 48 and an additional three of four persons with diarrhea were biopsied. All biopsies showed normal small intestinal mucosal architecture. All 1461 persons were negative for ARA. Our results demonstrate that AGA are frequently detected in an adult Estonian population and positivity increases with age in persons with normal small intestinal mucosa. Positivity for AGA does not predict silent undetected celiac disease but rather represents a normal response to dietary antigens in the elderly. Inability to detect ARA suggests that celiac disease does not exist in this population. As none of the AGA-positive but ARA-negative biopsied persons had celiac disease, ARA might be a more specific serologic marker for celiac disease than AGA.

Pancreatic and catalytic phospholipase A2 in relation to pregnancy, labor and fetal outcome

The serum pancreatic and catalytic phospholipase A2 level (PLA2) in human pregnancy is normal, and the increase of pancreatic enzyme before delivery is small. In patients with pruritus associated with obstetric hepatosis maternal serum had a slightly lower pancreatic PLA2 level if the cholic acid level was higher. Umbilical cord blood has twice as much pancreatic PLA2 as maternal blood. If the enzyme concentration was very high, pregnancies were postterm and the newborns had low Apgar scores. Amniotic fluid contains these enzymes, but there is no change in the enzymes during the course of pregnancy. The amount of pancreatic enzyme was not reflected in catalytic activity. A very high PLA2 activity was observed in 1 patient with suspected amniotic fluid embolism and in the meconium, but low in the first urine of neonates.