Relation between T cell number and epithelial HLA class II expression quantified by image analysis in normal and inflamed human gastric mucosa.

Epithelial expression of HLA class II determinants and the number of lamina propria and intraepithelial T cells were quantified in gastric body mucosa by means of paired immunofluorescence staining which was subjected to computerised image analysis. In normal mucosa, epithelial HLA-DR expression was virtually absent. A significantly increased expression was seen in simple chronic gastritis, most extensively in the isthmus zone, where a positive reaction was seen in 34% of the epithelial area when the gastritis was of low degree and in 85% when it was of moderate severity. The most extensive HLA-DR expression was found in moderate 'stump gastritis' 28 to 32 years after Billroth II resections. In these patients the epithelial area in the foveolar and isthmus zones showed 83% and 92% positive responses, respectively. The HLA subregion products were expressed in a differential manner (DR greater than DP greater than DQ). The number of both intraepithelial and lamina propria T cells increased significantly with increasing severity of gastritis, and the fraction of putative memory T cells was also raised. Correlation analyses showed a positive relation between the epithelial expression of HLA-DR and the intraepithelial as well as the lamina propria density of T cell. These results suggest a biological link between T cells, aberrant HLA-DR expression, and gastritis, although the pathogenic importance of this relation is unknown. Enhanced epithelial presentation of autoantigens or luminal antigens, or both leading to increased activation of T cells is one possible explanation.