Subsets of CD3+ (T cell receptor α/β or γ/δ) and CD3− lymphocytes isolated from normal human gut epithelium display phenotypical features different from their counterparts in peripheral blood

Intestinal intraepithelial lymphocytes (IEL) were studied, after isolation in humans for their surface antigens with a large variety of monoclonal antibodies. They show peculiar characteristics when compared with peripheral blood lymphocytes and intestinal laminapropria lymphocytes. Although a majority of human intraepithelial lymphocytes (IEL) express an α/β type of T cell receptor (TcR), 13% express a γ/δTcR, a percentage which was significantly higher than that found in blood and in lamina propria. In contrast to observations in mice, there was no evidence that normal human TcR γ/δ+ intestinal IEL might use preferential variable segments of γ genes. About 10% of human intestinal IEL expressed the α chain but not the β chain of CD8, thus resembling a subset of CD8 α+β− IEL, which was recently described in mice and found to be of thymoinde‐pendent origin. In addition, 10% of human IEL had a unique phenotype of immature T cells, as they bore only CD7, but no other T cell or natural killer cell markers. Finally, even the major population of IEL which expressed the usual markers of the T cell lineage (CD3,TcR α/β, CD2, CD4 or CD8 α/β) differed from peripheral blood T lymphocytes by their peculiar expression of surface antigens associated with activation. Indeed, 80% of IEL were CD45R0+, CD45A−, but co‐expression of CD11a, CD29 and LFA‐3 was inconstant. In addition, 90% of IEL expressed HML‐1.