Effect of IL-2 on immunoregulatory function of intestinal lamina propria T cells in normal non-human primates

The role of T cell activation on the immunoregulatory function of lymphocytes in the lamina propria of the normal intestine was investigated. Lymphocytes were isolated from different sites in non-human primates, and their cell surface phenotypes, response to exogenous IL-2, and immunoregulatory function in pokeweed mitogen stimulated cultures were determined. The proportions of Leu-3+ (CD4) and Leu-2+ (CD8) lymphocytes in isolated lamina propria cells were similar to peripheral blood and spleen, but the proportion of Leu-3+ cells was significantly higher in mesenteric lymph node lymphocytes. The proportion of IL-2 receptor positive cells was significantly higher in lamina propria compared with peripheral blood, spleen and mesenteric lymph nodes. Increased IL-2 receptor expression was found on both Leu-3+ and Leu-2+ lamina propria T cells. In addition, although lamina propria T cells had a lower proliferative response to Con A, they had a significantly higher response when cultured with recombinant IL-2, indicating that they have increased expression of functional IL-2 receptors. The helper function of lamina propria T cells for pokeweed mitogen stimulated immunoglobulin synthesis was enhanced by recombinant IL-2. Although Leu-2+ lymphocytes in the lamina propria had increased IL-2 receptor expression, suppressor function of lamina propria T cells was similar to that of spleen cells, and was not enhanced by addition of exogenous IL-2. Thus, T cells in the lamina propria have increased expression of functional IL-2 receptors, and recombinant IL-2 enhances the helper, but not the suppressor function of lamina propria T cells for immunoglobulin synthesis.