In crescentic glomerulonephritis, crescent formation involves the active participation of glomerular epithelial cells (GEC) and macrophages recruited to the glomerulus during the evolution of the disease. Cytokines derived from macrophages may affect many functions of GEC. In this study, we found that interleukin-1 beta (IL-1 beta) inhibited GEC growth (DNA synthesis and cell number) in vitro in a dose- and time-dependent manner. This effect was not mediated by tumor growth factor beta (TGF beta) which is a potent inhibitor of GEC growth in vitro. Treatment of GEC with various concentrations of IL-1 beta induced morphologic changes consisting in the loss of their cobblestone shape and acquisition of a fibroblast-like appearance. Moreover, IL-1 beta was shown to stimulate the expression of interleukin-6 (IL-6) by GEC. The increase in IL-6 secretion by GEC treated with IL-1 beta was observed at both the protein and mRNA levels. IL-1 beta also affected the metabolism of laminin in cultured GEC, inducing a dose-dependent increase in laminin production in culture supernatants harvested from GEC. Finally, we investigated the expression of MHC class II antigens and intercellular adhesion molecule-1 (ICAM-1) in GEC, and found that unstimulated GEC are negative for MHC class II antigens, as detected by flow cytometry. In contrast to the induction of effector functions, expression of MHC class II antigens stringently required interferon-gamma. IL-1 beta did not induce MHC class I antigen expression. The regulation of ICAM-1 expression in that unstimulated GEC expressed ICAM-1, and this expression was upregulated by IL-1 beta. We conclude that IL-1 beta alters many functions of GEC, and these changes may be involved in the initiation and amplification of glomerular injury.