We have shown previously that rat liver macrophages (Kupffer cells) express a membrane-bound form of C-reactive protein (mCRP) on their surface which is identical to a galactose-specific particle receptor activity. We now establish the presence of mCRP on human monocyte-macrophages using immunocytochemistry with an anti-neoCRP specific monoclonal antibody and RNA-RNA in situ hybridization to demonstrate the presence of CRP-specific mRNA. Concomitant with mCRP expression, cells exhibit galactose-dependent uptake of particles coated with lactosylated bovine serum albumin. Adhesion experiments on fibronectin-coated surfaces that mCRP on human blood monocytes may act as a selectin-like adhesion molecule, mediating initial carbohydrate-specific contacts which are followed by peptide-specific recognition via integrin receptors.
We could recently show that rat liver macrophages (Kupffer cells) express a membrane-bound form of C-reactive protein on their surface. Because it is removed by washing the cells in buffers containing Ca(++)-chelators, membrane-bound C-reactive protein is a peripheral protein rather than an integral part of the Kupffer cell membrane. This Kupffer cell membrane-bound C-reactive protein is identical to the galactose-specific particle receptor previously characterized. We now present evidence that Kupffer cells do not acquire soluble serum C-reactive protein but synthesize their own membrane-bound C-reactive protein. By RNA-RNA in situ hybridization, it was found that hepatocytes are not the only sort of liver cells synthesizing C-reactive protein, but C-reactive protein-specific mRNA is present also in Kupffer cells. During acute-phase response C-reactive protein mRNA is found in increased amounts within liver macrophages too. Furthermore, by labeling experiments with antisera against native, pentameric soluble serum C-reactive protein and monoclonal antibodies against a neoepitope present on C-reactive protein subunits only, we could establish that the membrane-bound C-reactive protein expressed on the liver macrophage is not the pentameric molecule of soluble serum C-reactive protein, but rather consists of C-reactive protein subunits. Finally, we present evidence that liver macrophages contain a binding protein in their plasma membrane, with an apparent molecular weight of 59 to 61kD, specific for C-reactive protein and similar to the one previously isolated from macrophage cell lines.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.