NUMBER, FIXATION PROPERTIES, DYE-BINDING AND PROTEASE EXPRESSION OF DUODENAL MAST-CELLS - COMPARISONS BETWEEN HEALTHY-SUBJECTS AND PATIENTSWITH GASTRITIS OR CROHNS-DISEASE

There is an accumulation of evidence to suggest that mast cells may pl ay a key role in gastrointestinal inflammation. We have investigated t he numbers and heterogeneity in staining properties of mast cells in b iopsies of the duodenum of normal subjects (n = 10), and of normal duo denum from patients with Crohn's disease of the ileum and/or colon (n = 7) or with Helicobacter-associated gastritis of the antrum/corpus (n = 6). In normal donors, two subsets of mast cells, one located in the duodenal mucosa and the other in the submucosa, were clearly distingu ished by their morphology and dye-binding properties. Whereas submucos al mast cells stained metachromatically with Toluidine Blue after neut ral formalin fixation and emitted a yellow fluorescence after staining with Berberine sulphate, those in the mucosa were invisible using the se stains. In patients with gastritis or Crohn's disease, there were m arked changes in the numbers of mucosal mast cells compared with contr ol subjects, even though the duodenal biopsies were from apparently un involved tissue. Gastritis was associated with increased mucosal mast cell numbers (controls: 187 +/- 23 cells mm(-2); gastritis: 413 +/- 13 9 cells mm(-2); p = 0.0004), but mean mucosal mast cell counts in the uninvolved duodenum of Crohn's patients were actually decreased (34 +/ - 30 cells mm(-2), p = 0.0147). The clear differentiation between muco sal and submucosal mast cells on the basis of metachromasia with Tolui dine Blue was not seen in biopsies from the patients with gastritis or Crohn's disease. Previous studies which have suggested that there are no distinct mucosal and submucosal mast cell subsets in the human int estine may, therefore, have been affected by the use of tissue from di seased subjects. Heterogeneity in the expression of mast cell tryptase and chymase was seen by immunohistochemistry using specific antibodie s, but the relative numbers of mast cell subsets were critically depen dent on the methods used. Using a sensitive staining procedure, the ma jority of mucosal mast cells stained positively for chymase as well as for tryptase, an observation confirmed by immunoelectron microscopy a nd immunoabsorption studies. Our findings suggest that early stages in intestinal inflammation may be reflected in changes in mast cell numb ers and in their staining properties, and call for a reappraisal of ma st cell heterogeneity in the human intestinal tract.