Fibrinogen / Fibrin on the Surface of Macrophages : Detection , Distribution , Binding Requirements , and Possible Role in Macrophage Adherence Phenomena

After intraperitoneal (i.p.) injection of antigen into guinea pigs primed for delayed hypersensitivity, peritoneal macrophages adhere to each other and to the peritoneal serosal cells (1-3). This phenomenon, termed the macrophage disappearance reaction (MDR)' by Nelson, is inhibited by warfarin or heparin (2) and is mimicked by i.p. administration of thrombin to unsensitized animals (4). Although these data suggest that macrophage adherence may be mediated by activation of the clotting system, initial attempts to identify fibrin on macrophages by electron microscopy were unsuccessful (3). Because fibrin depo-sition has recently been shown to be a characteristic feature of classic cell-mediated hypersensitivity reactions in guinea pigs and man (5, 6), we have reexamined the possibility that mononuclear cells might interact directly with fibrinogen or fibrin (Fib). By means of immunofluorescent techniques, we have found that a substantial population of peritoneal mononuclear cells have a particular avidity for binding Fib to their cell surface. Materials and Methods Cell Preparation. Normal, 300-500 g male Hartley guinea pigg2 were lightly anesthetized with ether, exsanguinated by cardiac puncture, and the peritoneal cavities lavaged with 100 ml of ice-* Portions of this work were presented in abstract form at the 59th Annual Meeting of the arginine methyl ester. z In conducting the research described in this report, the investigators adhered to the "Guide for Laboratory Animal Facilities and Care," as promulgated by the Committee on the Guide for