Intraepithelial lymphocytes of human gut: isolation, characterisation and study of natural killer activity.

A method using a mechanical procedure for isolation of lymphocytes from the epithelium of human intestinal mucosa allows the study of some of their characteristics and functions. Most of the isolated cells are of the T lineage (E+ and T3+) and express the phenotype associated with cytotoxic-suppressor T cells (T8). A large number contain intracytoplasmic granules. Granules are stained with alcian blue (pH 2.2), are metachromatic with Toluidine blue (pH 4) and some are shown to incorporate 35sulphate, suggesting that they contain sulphated mucopolysaccharides. As these cells are similar in many respects to the large granular lymphocytes that mediate natural killer activity in the peripheral blood, their natural cytotoxicity was tested against K 562 target cells. No activity was detected among the human intraepithelial lymphocytes and treatments with known potentiators of natural killer activity, ie, interferon or PHA-depleted conditioned medium containing Il-2, failed to reveal any cytotoxic activity.