Interleukin-7 activates intestinal lymphocytes

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Abstract
Human intestinal lymphocytes, particularly intraepithelial lymphocytes, proliferate minimally to some agents, like mitogens and stimuli of the CD3 pathway. Thisin vitro finding may be due, in part, to a loss of factors foundin 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 propria lymphocytes proliferated more vigorously to IL-7 than to IL-9 or 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 subsets responded to this cytokine as shown by phenotype-depletion experiments and constancy in the CD4/CD8 ratios after culture with IL-7. In addition, the T-cell receptor αβ and γδ subsets responded equally well to IL-7. This newly described selective proliferative response of intestinal lymphocytes to IL-7, but not to IL-9 or IL-12, requires no preactivation and may enhance, growthin vivo.