Analysis of natural killer effector and suppressor activity by intraepithelial lymphocytes from mouse small intestine

Intraepithelial lymphocytes (IEL) are morphologically similar to NK cells in other tissues and we have studied the NK activity of IEL isolated from mouse small intestine. In contrast to spleen NK cells, IEL showed little activity against YAC-1 over 4 h but had high levels of NK activity when the assay was extended to 18 h. IEL from nude mice did not show the enhanced NK activity found in other tissues. IEL were also found to suppress the NK activity of spleen cells and this suppressor function was not mediated by T lymphocytes or macrophages. The results indicate that the intestinal epithelium contains a population of potent NK cells which may represent a type of NK cell different to that found in other tissues. In addition, there are also cells capable of regulating NK cell function in the epithelial layer.