INTERLEUKIN-7 ACTIVATES INTESTINAL LYMPHOCYTES

Human intestinal lymphocytes, particularly intraepithelial lymphocytes , proliferate minimally to some agents, like mitogens and stimuli of t he CD3 pathway. This in vitro finding may be due, in part, to a loss o f factors found in vivo. Three T-cell growth factors, IL-7, IL-9, and IL-12, were tested for their ability to stimulate the proliferation of intestinal lymphocytes. Both intraepithelial lymphocytes and lamina p ropria lymphocytes proliferated more vigorously to IL-7 than to IL-9 o r IL-12, and only IL-7 increased stimulation through the CD3 pathway. The IL-7-induced response was IL-2-dependent: IL-2 receptors appeared on both intestinal lymphocyte types, and antibody to the IL-2 receptor blocked IL-7-induced proliferation. Both CD4(+) and CD8(+) T-cell sub sets responded to this cytokine as shown by phenotype-depletion experi ments and constancy in the CD4/CD8 ratios after culture with IL-7. In addition, the T-cell receptor alpha beta and gamma delta subsets respo nded equally well to IL-7. This newly described selective proliferativ e response of intestinal lymphocytes to IL-7, but not to IL-9 or IL-12 , requires no preactivation and may enhance growth in vivo.