The receptor for interferon-gamma on human peripheral blood monocytes consists of multiple distinct subunits. |
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Authors: | D S Finbloom L M Wahl K D Winestock |
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Institution: | Division of Cytokine Biology, Food and Drug Administration, Bethesda, Maryland 20892. |
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Abstract: | The interaction of interferon-gamma (IFN gamma) (a product of activated T lymphocytes) and monocytes is essential for immune responsiveness, host defense, and chronic inflammation. In this report we define the IFN gamma receptor (IFN gamma R) on human monocytes as a receptor complex consisting of at least three subunits. Solubilization and immunoprecipitation of 35S]methionine- and 35S]cysteine-labeled monocytes were optimized by controlling the detergent concentration during solubilization and washing of the immunoprecipitates. This enabled subunits to be coimmunoprecipitated by several different anti-IFN gamma R antibodies raised against the 90-kDa cloned binding protein. Immunoprecipitation under stringent (1% sodium dodecyl sulfate) conditions resulted in the visualization of only the 80-90-kDa binding protein. Under less stringent conditions at least two coimmunoprecipitated subunits (molecular mass of 200 and 38 kDa) were consistently associated with the 80-kDa (90-92 kDa reduced) binding protein. The 38-kDa subunit was shown to be distinct from the 80-kDa subunit by proteolytic fragment analysis. Cross-linking of 125I-rIFN gamma to monocytes yielded receptor-IFN gamma complexes consistent with the existence of multiple subunits. |
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