Regional variations in the number and subsets of intraepithelial lymphocytes in the mouse small intestine

Background and Purpose: Regional variations in the intraepithelial lymphocy tes (IELs) in the mouse small intestine were examined. Methods: The small intestine was taken from six 12-week-old BALB/c mice and divided equally into three parts (proximal, middle, and distal). The IELs were isolated from each part of the intestine and analyzed by use of flow c ytometry. Results: The number of IELs in the distal part of the small intestine was s ignificantly lower than that in the proximal and middle parts (P < 0.01). T he distribution of IEL subsets was markedly different between the proximal and the distal parts, and that in the middle part had an intermediate patte rn. The percentage of alpha beta T cells and expression of Thy-1.2 on the a lpha beta T and gamma delta T cells were higher in the distal part (P < 0.0 1). The percentage of CD8 alpha alpha and of double-negative T cells were h igher in the proximal part, whereas that of CD4CD8 alpha alpha double-posit ive T cells was higher in the distal part (P < 0.01). Regional variations w ere found mainly in the extrathymically developed T cell subsets. Conclusion: Local development of IELs may differ between regions of the sma ll intestine.