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Expression of membrane-associated C-reactive protein by human monocytes: indications for a selectin-like activity
V Kolb-Bachofen1, N Puchta-Teudt, C Egenhofer
1Institute for Immunobiology, Medical Faculty, Heinrich-Heine-University Düsseldorf, Germany.
Abstract:
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.
Insights
Human monocyte-macrophages express membrane-bound C-reactive protein (mCRP), acting as a galactose-specific receptor. This mCRP mediates initial cell adhesion, similar to selectins, facilitating interactions before integrin binding.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Kupffer cells (rat liver macrophages) express membrane-bound C-reactive protein (mCRP) with galactose-specific receptor activity.
- The function and presence of mCRP on human macrophages were previously uncharacterized.
Purpose of the Study:
- To establish the presence of mCRP on human monocyte-macrophages.
- To investigate the functional role of mCRP in human monocyte adhesion and particle uptake.
Main Methods:
- Immunocytochemistry using an anti-neoCRP monoclonal antibody.
- RNA-RNA in situ hybridization to detect CRP-specific mRNA.
- Galactose-dependent particle uptake assays.
- Cell adhesion experiments on fibronectin-coated surfaces.
Main Results:
- Human monocyte-macrophages express mCRP and CRP-specific mRNA.
- Cells exhibit galactose-dependent particle uptake when coated with lactosylated bovine serum albumin.
- mCRP on monocytes mediates initial carbohydrate-specific adhesion, preceding integrin-mediated recognition.
Conclusions:
- Human monocyte-macrophages express mCRP, functioning as a galactose-specific receptor.
- mCRP acts as a selectin-like adhesion molecule on human monocytes, initiating cell-surface interactions.
- This mechanism highlights a novel role for CRP in immune cell adhesion and recognition.