An approach to the characterization of mononuclear phagocytes involved in pathological processes.

Cells participating in an inflammatory response are derived from the bone marrow (i.e. granulocytes and monocytes) or lymphoid organes (i.e. T and B lymphocytes), or of mesenchymal origin (i.e. fibroblast, reticulum cells). The identification of these different kinds of cell in the inflammatory exudate is often difficult, because the morphological characteristics are not specific enough. For example, in the morphological description of pathological processes often terms such as round-cell infiltration and mononuclear cells are used, which is confusing. For the clear understanding of the course of an inflammatory reaction and the effect of anti-inflammatory drugs it is necessary, however, to define exactly the participating cells. Such an identification can be performed on the basis of morphological, cytochemical and immunological characteristics of the cells, together with their kinetic parameters. These characteristics have been established for murine mononuclear phagocytes. Recently these characteristics have also been studied in human promonocytes, monocytes and skin macrophages. The results show that human mononuclear phagocytes are in many respects similar to those of mice. On this basis an outline for the participation of mononuclear phagocytes in pathological processes (i.e. inflammatory processes, neoplastic processes, and storage disorders) has been made.