SEPHADEX(R) INDUCED GRANULOMATOUS REACTION IN RATS

Granuloma formation in the rat lung after single or repeated i.v. inje ctions, intratracheal instillation and intradermal implantation of Sep hadex(R) beads was studied over a time period from 3 h to 3 mo. Macrop hages were identified with the mAB ED1, vascular smooth muscle cells w ith an mAB against cr. SMC-actin, endothelial cells with a polyclonal AB against factor VIII and cyclic activity with an mAB against PCNA. T he morphology and the time course of the development of the granulomas is identical in the different experimental conditions. The macrophage s form the bulk of the cellular infiltrates, giant cells appear after 24 h. Cyclic activity is early and marked in the interstitially locate d macrophages, it is delayed and slight around the beads, suggesting a biphasic pattern. The macrophage reaction is markedly enhanced after a second i.v. injection, indicating the development of a hypersensitiv ity state. Numerous eosinophils are located in the interstitium, but o nly few are in direct contact with the beads. Their number doesn't inc rease after a second i.v. injection. Intradermal implantations show on ly macrophages and lymphocytes. A special feature is the disappearance of the arterial wall around the beads resulting in extrusion without haemorrhages or thromboses.