Background: The number of intraepithelial lymphocytes in the duodenum was determined 30 years ago, the suggested normal upper limit being 40 lymphocytes per 100 epithelial cells.
Methods: Duodenal mucosa was analysed from 18 healthy individuals and 56 consecutive patients biopsied because of epigastralgia (17 cases), diarrhoea (10 cases), oesophagitis (10 cases), iron-deficiency (9 cases) and B12-deficiency (10 cases) showing normal histology, along with 10 cases of active coeliac disease. The biopsies were fixed in 4% formalin overnight and embedded in paraffin. Three micrometre thick sections were stained with haematoxylin and eosin and CD3. At least 300 epithelial cells were counted, the number of intraepithelial lymphocytes was given as the mean/100 epithelial cells. Extensive statistical analyses were performed.
Results: In the healthy individuals the mean number (s) of intraepithelial lymphocytes/100 epithelial cells was 10.8 (2.6) and 13.2 (3.8) in H&E and CD3 stained sections, respectively. The upper limit of the confidence interval for CD3 staining was 29. There was no significant difference between normal individuals and the clinical groups, with the exception of coeliac disease.
Conclusion: Two-step analysis of intraepithelial lymphocyte-determination is suggested: (a) semi-quantitative estimate on H&E-stained sections (normal ratio of 1:5 between lymphocytes and enterocytes; upper normal limit 20 lymphocytes) and (b) CD3-staining and counting if intraepithelial lymphocytosis is suspected. The upper normal range of intraepithelial lymphocytes is set at 25 CD3+ lymphocytes/100 epithelial cells. Values between 25 and 29 are regarded as 'borderline' and 30 or more represent pathologic intraepithelial lymphocytosis in the duodenum.