The relationship between anti-endomysium antibodies and villous atrophy in coeliac disease using both monkey and human substrate.

BACKGROUND/OBJECTIVE: Circulating antibodies offer a noninvasive diagnostic screening test in patients with coeliac disease with severe histopathological abnormalities. This study assesses for the first time the sensitivity and reliability of anti-endomysium in screening for coeliac disease in patients with milder forms of villous atrophy using human umbilical cord and monkey ileum. MATERIALS AND METHODS: Serum from 124 adults and children > 2 years old including 33 patients with coeliac disease on a gluten-free diet and 91 patients referred to the laboratory for screening was studied. The presence of IgA-anti-gliadin (AGA) (ELISA) and IgA-anti-endomysium (EMA) was detected in the serum using monkey ileum and human umbilical cord (HUC) substrates. Patients with abnormal serology results or severe clinical complaints were invited to attend for a small-bowel biopsy. The prevalence of EMA detected on monkey ileum and HUC was compared with the histopathological features of coeliac disease at presentation. Fifty-three of the 91 patients screened for coeliac disease underwent a small intestinal biopsy. RESULTS: Twenty-three of the 91 patients suspected of having coeliac disease had coeliac disease. The EMA test was positive in 18 of 23 using both monkey ileum and HUC (sensitivity 78%). Partial villous atrophy (PVA) was seen in four of the five EMA-negative patients, and subtotal/total villous atrophy (SVA/TVA) was demonstrated in 18 of the 23 cases with positive EMA. Both substrates detected identical positive cases. There was an excellent concordance between EMA sensitivity evaluated on HUC and those on monkey ileum. One patient was EMA-negative on monkey ileum but positive on HUC and one patient who was EMA-positive on monkey ileum was EMA-negative on HUC. Only one of 33 coeliac disease patients on gluten-free diet for more than one year with persisting TVA had positive EMA. The rest of the cases had a negative EMA on both HUC and monkey ileum. CONCLUSION: A negative result for EMA in coeliac disease patients with a normal IgA value does not exclude the diagnosis of coeliac disease. A positive EMA is seen mostly in those coeliac disease patients with severe tissue damage (SVA/TVA). EMA has a low sensitivity in coeliac disease patients with PVA in spite of use of different substrates.

Sensitivity of antiendomysium and antigliadin antibodies in untreated celiac disease: disappointing in clinical practice.

OBJECTIVE: We have undertaken a study to assess the efficiency of serological tests in the diagnosis of celiac disease (CD) during the period January 1, 1994 to January 7, 1997. Our aim was to evaluate the sensitivity of IgA antiendomysium (EMA) and IgA antigliadin (AGA) with regard to the degree of histological abnormality in biopsy specimens of small intestine in untreated celiac disease patients and first-degree relatives. METHODS: The study population comprised 101 cases: 85 untreated celiac patients and 16 first-degree relatives with a mean age of 42 yr (range, 2-76 yrs). Sixteen of 85 were excluded from study because they did not satisfy the study or diagnostic criteria of CD. EMA and AGA have been compared with the degree of villous atrophy (VA) in 69 celiac patients and 16 relatives according to the Marsh criteria of 1992. We divided the Marsh III histology into three subgroups as follows: Marsh IIIa (partial VA), Marsh IIIb (subtotal VA), and Marsh IIIc (total villous atrophy). RESULTS: The specificity and positive predictive value of EMA for CD was excellent, because all EMA-positive patients (n = 42) were diagnosed with CD. The sensitivity of EMA, however, differed between CD subgroups; in patients with total VA, the sensitivity of EMA was 100% (17/17). However, in patients with partial VA (Marsh IIIa), the sensitivity of EMA was disappointing, only 9/29 (31%). Three of 72 celiacs with Marsh IIIb and Marsh IIIc had IgA deficiency and were excluded from the study. Elevated AGA has been detected in the sera of 39 of 69 (62%) patients. A combination of EMA and AGA tests showed a sensitivity of 76% (53/69). None of 16 first-degree relatives with Marsh I-II had positive EMA. CONCLUSIONS: Interpretation of negative serology needs great awareness. Although EMA sensitivity in total villous atrophy is excellent, in partial villous atrophy the sensitivity of EMA appears to be disappointing. Our experience shows that EMA and AGA have only limited value in screening programs for CD.

Relation between effects of a set of anti-allergic drugs on calcium pathways and membrane structure in Fc epsilon RI activated signal transduction.

The antigen induced stimulation of mast cells by aggregation of Fc epsilon RI receptors activates a signal transduction cascade leading to release of mediators of inflammation like histamine, arachidonic acid metabolites and cytokines. In this study we investigated a series of structurally related anti-allergic drugs, containing a common lipophilic diphenylmethyl piperazinyl tail and head groups that differ in lipophilicity. Effects of these drugs on various steps of the signal transduction cascade was investigated to gain insight into the mechanism of action of these drugs. It appeared that addition of the drugs to resting cells induced changes in the tyrosine phosphorylation of cellular proteins. The most active anti-allergics in inhibiting exocytosis, AL3264 and oxatomide, also induced the largest changes in phosphorylation. The effects of the drugs on tyrosine phosphorylation after cell activation was complex. Additionally, Ca2+ fluxes were investigated. Ca2+ efflux from the cells was negligibly influenced by the active drugs. However, the drugs inhibited influx from extracellular Ca2+, which was correlated with the effects of the drugs on inhibition of exocytosis and on membrane stabilization induced by the drugs, measured as haemolysis of erythrocytes. It is concluded that inhibition of Ca2+ influx is the major mechanism with which these drugs inhibit exocytosis and that for this effect drug-membrane interactions, possibly affecting the function of membrane embedded proteins, are of importance. Possible mechanisms including drug-membrane interactions, phosphorylation and inhibition of Ca2+ influx are discussed.

Influence of the anti-allergic drug oxatomide on the signal transduction mechanism in a mast cell model.

In a mast cell model, oxatomide displays inhibition of mediator release which is not related to its histamine H1 receptor antagonistic activity. From a previous study it appeared that especially early steps in the signal transduction leading to exocytosis were influenced by oxatomide. We now studied effects of oxatomide on those early steps in more detail. The antigen- and thapsigargin-mediated exocytosis in rat basophilic leukemia (RBL-2H3) cells were both inhibited by oxatomide. After aggregation of high affinity receptors for immunoglobulin E (Fc epsilon RI), protein tyrosine phosphorylation is induced. Oxatomide caused remarkable changes in the tyrosine phosphorylation pattern in resting cells. Also after antigen and thapsigargin activation, changes in the tyrosine phosphorylation of cellular proteins are observed. In addition, Ca2+ fluxes were studied by means of the net influx of 45Ca2+ and by measuring intracellular free Ca2+ concentrations ([Ca2+]) with the fluorescent probe fura-2. Oxatomide inhibited the 45Ca2+ influx and the increase in [Ca2+]i upon antigen and thapsigargin activation of the cells. Neither the release of Ca2+ from internal stores nor the efflux of Ca2+ over the plasma membrane seems to be affected. The effect of oxatomide on Ca2+ influx was further characterized by studying Ba2+ influx in the absence of extracellular free Ca2+. We conclude that inhibition of mediator release is mainly caused by inhibition of influx of extracellular Ca2+, via plasma membrane Ca2+ channels that are activated by depletion of intracellular Ca2+ stores. The molecular mechanism with which oxatomide might interfere with these channels is discussed.