A model of human cytokine regulation based on transfection of γ interferon gene fragments directly into isolated peripheral blood T lymphocytes

Abstract

An approach has been optimized permitting measurement of human cytokine reporter gene expression after transient transfection directly into purified human peripheral blood T lymphocytes. Comparing the expression of interleukin 2 (IL-2) CAT with a series of specially engineered γ interferon (IFN-γ) constructs, a fundamental difference in the molecular mechanisms regulating these two cytokines has been suggested. A potent, tissue-specific, constitutive-acting positive regulatory element was located between sequences -215 and -53 in the human IFN-γ gene. Deletion analyses suggested that sequences slightly upstream, between positions -251 to -215, exerted a powerful dominant suppressive influence over that positive element. Negative elements appear to play a major role in controlling the regulation of human IFN-γ gene expression. We thus propose a model of cytokine gene regulation in which selective derepression may be an important fundamental mechanism of induction and/or positive modulation.