Philip H. Prose

Culture of adult human skin: in vitro growth and keratinization of epidermal cells.

ADULT human skin has been successfully cultured by several methods, but progress has been slow because the cells in the outgrowth have never been satisfactorily identified. Light microscopy has shown that fibroblasts grown on glass surfaces may assume a pavement-like appearance and mimic the growth pattern of epithelial cells1. To avoid this, several investigators have attempted to eliminate fibroblasts from growing cultures1–4. In none of these experiments was it conclusively shown that growing cells are epithelial and undergo keratinization, although these assumptions appear to be valid.

The extravascular nature of Arthus reactions elicited by ferritin. A combined light and electron microscopic analysis of immune states in rabbit ear chambers and mesenteries.

SummaryRabbits were immunized with ferritin and were challenged with the antigen (1) by placing the ferritin on top of rabbit ear chamber tissue and (2) by placing it on top of immune mesentery. In immune animals, a brisk and mounting reaction was characterized by white blood cell sticking and emigration, thrombosis, stasis, vessel shutdown and necrosis. Electron micrographs of tissue taken from sites of injury revealed aggregates of electrondense material with a double density. The material appeared in the extravascular tissue, often perivascularly, inside and outside of white blood cells, the cells being virtually exclusively polymorphonuclear leucocytes. The clumps, presumably antigen-antibody complexes, were never found intraluminally. Ferritin was not found phagocytized by endothelial cytoplasm.The evidence permits the hypothesis that such reactions have their genesis in the extravascular deposition of immune complexes, not in the vessel wall as many observers have held.It is possible, however, that this may be a property of electron-dense high molecular antigens, such as ferritin, and not necessarily a general characteristic of reactions associated with hypersensitivity states of the Arthus type or of other types.It is the purpose of this communication to present the evidence that in the genesis of the Arthus reaction, the site for the reactants is in the extravascular tissue, not in the vessel wall. Subsequently, blood vessel injury occurs and, with it, the exudative phase of the reaction. This does not diminish the importance of the polymorphonuclear leucocyte in the reaction but, in perspective, it identifies white cell sticking and emigration, and endothelial injury, as relatively late events in the phenomenon. The evidence suggests that the early events of the Arthus reaction may involve white blood cells that have emigrated across capillary beds and are present in extravascular tissue before the stimulus provided by immune reactants. Such an hypothesis offers a unifying concept for the phenomenon and, if valid, explains many of the apparently disparate experimental facts surrounding the Arthus reaction.