The product of the human IFN-gamma gene was found to be a powerful upregulatory stimulus for its own gene expression in lectin-activated human PBMC. The INF-gamma autosuperinduction response was further enhanced by "priming" PBMC with IFN-gamma. Primed cells maximally upregulated their levels of IFN-gamma specific mRNA 4-fold faster and more than 20-fold higher than mock-stimulated cells. High mRNA levels persisted for several days after stimulation, and enhanced secretion of biologically active IFN-gamma paralleled the observed upregulation of gene expression. Producer cells demonstrating this response were found to be primarily localized to the rosette E- (leu 11+) fraction of PBMC and appear to be of the LGL/NK variety. Whether the autosuperinduction phenomenon occurs through direct or indirect effects of IFN-gamma on producer cells is still unclear. These results may be important both to an understanding of the pathogenesis of immune dysfunction and to the design of more effective immunotherapy.