The effect of lymphokines on macrophage accumulation and disappearance in the peritoneal cavity.

The intraperitoneal injection of antigen into delayed hypersensitive animals or of preformed lymphokines into unimmunized animals can lead to changes in the distribution and content of inflammatory cells within the peritoneal cavity. If a preexisting macrophage-rich exudate is present, then these challenges will lead to a diminution of the number of macrophages recoverable (macrophage disappearance reaction, MDR). If the peritoneal cavity has been unprepared, then the same stimuli will lead to an increase in the number of macrophages (macrophage appearance reaction, MAR). The existence of opposite effects that can be produced at a given site by the same stimuli provides insights into the multiple interactions involved in biologic reactions mediated by complex mixtures of mediators. Such factors include, in addition to the reaction site itself and the kinds of mediators present, both qualitative and quantitative aspects of the target cell population.