Effects of cytokines on human thymic epithelial cells in culture: IL1 induces thymic epithelial cell proliferation and change in morphology

The role of thymic epithelium in T cell development has given rise to a number of studies, but less information is available concerning the factors regulating thymic epithelial cells (TEC) themselves. Several cytokines, natural or recombinant, were investigated for their effects on human TEC proliferation. This study presents evidence for the first time that human recombinant interleukin 1 (IL1) and IL1-containing mixed cytokine preparations induced DNA synthesis of TEC as measured in a 48-hr stimulation assay. The effects of IL1 were dose dependent and sustained in time. The following recombinant cytokines, IL2, IL3, IL4, interferon-gamma (IFN-gamma), IFN-alpha, tumor necrosis factor-alpha (TNF alpha), and TNF beta, as well as thymosin fraction 5 and Escherichia coli lipopolysaccharide (LPS), were not found to modify TEC proliferation but IFN-gamma and TNF alpha enhanced the effects of IL1. We also report that IL1 induced a profound change in the morphology of TEC. Our observations suggest that TEC are targets for the action of cytokines and emphasize the important role played by IL1 within the thymus.