Human intestinal mononuclear cells. II. Demonstration of a naturally occurring subclass of T cells which respond in the allogeneic mixed leukocyte reaction but do not effect cell-mediated lympholysis.

We have examined the T-cell functional capabilities of human intestinal mononuclear cells isolated from surgically obtained normal and inflammatory bowel disease intestinal specimens. Intestinal mononuclear cells have T cells present which respond to the mitogenic lectins E-PHA, Con A, and PWM and to foreign cell-surface antigens in the allogeneic-mixed leukocyte reaction. Intestinal mononuclear cells from ulcerative colitis patients exhibit a significantly decreased responsiveness in comparison to normal intestinal mononuclear cells with regard to both mitogenesis and the allogeneic-mixed leukocyte reaction; however, these defects may be secondary to the severity of the disease process that led to intestinal resection or the therapy which patients had received. Although both normal and inflammatory bowel disease intestinal mononuclear cells exhibit responsiveness in the allogeneic-mixed leukocyte reaction, thus indicating recognition of and sensitization by foreign cell-surface determinants, intestinal mononuclear cells do not subsequently kill the sensitizing cells in cell-mediated lympholysis. Therefore, the subclass of T cells which mediates cell-mediated lympholysis may either be absent from intestinal mononuclear cells or nonfunctional, while the subclass of T cells which responds in the allogeneic-mixed leukocyte reaction is both present and functional. This observation adds to the evidence of major functional differences between intestinal and peripheral blood mononuclear cells. Therefore, it will be necessary to better understand the factors regulating the effector capabilities of intestinal mononuclear cells before delineation of immunopathologic events in these tissues.