Glycolipids of the Mouse Peritoneal Macrophage

The macrophage participates in a wide variety of important physiological functions, including the recognition and destruction of tumor cells. Since many of these functions are mediated by the cell surface, the structural and functional characterization of macrophage surface components is an area of considerable interest and intense study (I-3) . One approach to this study involves analyzing alterations in macrophage surface components that occur in response to inflammation or as a consequence of activation to a tumoricidal state (1-4). Information obtained from studying these alterations has proven useful in identifying specific components that are involved in some of the specialized surface functions characteristic of the inflammatory and the activated macrophage. To date, most work in this area has focused on protein components of the macrophage surface, particularly on receptor proteins. Although much has been learned from these studies, other potentially important components have not been studied in detail. Glycolipids constitute one class of surface components for which biochemical data are scant. An increasingly large body of evidence indicates that glycolipids are important functional components of the cell surface (5); for this reason, it seems likely that glycolipids may play key roles in macrophage surface phenomena, either by themselves, or in concert with other surface components. The limited data that do exist on macrophage glycolipids, however, are f ragmented and contradictory. For example, there are reports that argue both for (6) and against (7) the presence on the macrophage surface of asialo GM~, a molecule of considerable importance, since it has been implicated as a marker for specific types of cytotoxic cells (8). In light of the above observations we have carried out a detailed study on the major glycolipid constituents of the resident, inflammatory, and tumoricidally activated mouse peritoneal macrophage. The results presented in this paper demonstrate that the inflammatory and the activated macrophage are characterA. M. M. is a Medical Foundation (Boston, MA) Research Fellow. This work was supported also by National Institutes of Health Postdoctoral Fellowship EY05487 (to A. M. M.), and NIH Grants CA25532 (to G. A. S.) and CA26712 (P. W. R.). Structures of the glycolipids referred to in this paper are presented in Table I.