Localization and phenotype of CD3 associated gamma/delta receptor expressing intestinal intraepithelial lymphocytes.

This study was carried out to determine the exact phenotype and localization of intestinal intra epithelial lymphocytes (IEL). IEL reside in the small intestine between or just beneath the epithelial cell layer which covers the lamina propria. These CD3 positive cells were found in equal numbers at this location both in the villi as well as in the crypts. The majority of these cells express a CD3 associated gamma delta receptor. Cell surface marker analysis of isolated IEL reveals high percentages of cells expressing CD8 and/or Thy-1. No CD4 positive cells could be detected in significant numbers. Equal quantities of IEL could be isolated from the intestine of athymic (nude) mice. Although the percentage of CD3 positive cells in the IEL from nude mice was lower than the figures obtained from euthymic mice northern blot analysis revealed a strong expression of gamma delta message in the IEL of nude mice. In the CD3 positive IEL fraction of nude mice the relative contribution of the CD8 positive cells remained unchanged, whereas the percentage of Thy-1 positive cells had decreased. Still significant numbers of such cells could be demonstrated in the IEL of nude mice. Altogether these results show that, at least, a significant part of the gamma delta receptor bearing IEL is independent of the thymus for their differentiation.