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MRC OX-45 antigen: a leucocyte/endothelium rat membrane glycoprotein of 45,000 molecular weight
Abstract:
Monoclonal antibodies MRC OX-45 and OX-46 detect identical or juxtaposed antigenic determinants on a novel rat membrane molecule that plays a possible role in macrophage suppression of antigen-induced T-cell responses. These antibodies react with most mature hematopoietic cells and their bone-marrow precursors, vascular endothelium and some connective tissue. The OX-45 antigens were purified from brain (mainly endothelium) and spleen by immunoaffinity chromatography, and were found to be glycoproteins with apparent Mr 43,000 and 45,000, respectively, as determined by SDS-PAGE analysis. The amino acid compositions of the two preparations were very similar but with no distinguishing features. The broad pattern of distribution was not the result of fortuitous cross-reaction of the MAbs as a single N-terminal sequence was obtained from mixed spleen populations of cells. Carbohydrate compositions of the brain and spleen molecules differed both in absolute amount (22 and 41% by weight, respectively) and in the ratios of various saccharides reflecting overall differences in the patterns of glycosylation between the two tissues. MRC OX-45 IgG showed an heterogeneity in the Mr of its H chain due to the attachment, in some molecules, of carbohydrate structures to the Fd fragment.
Insights
Monoclonal antibodies identified a novel rat membrane molecule involved in suppressing T-cell responses. This molecule, a glycoprotein found on various cells and tissues, exhibits distinct glycosylation patterns.
Area of Science:
- Immunology
- Molecular Biology
- Cell Biology
Background:
- Monoclonal antibodies MRC OX-45 and OX-46 recognize a novel rat membrane molecule.
- This molecule may regulate macrophage suppression of T-cell responses.
- The antibodies react with hematopoietic cells, endothelium, and connective tissue.
Purpose of the Study:
- To characterize the novel rat membrane molecule.
- To investigate its role in immune responses.
Main Methods:
- Immunoaffinity chromatography for antigen purification.
- SDS-PAGE analysis for molecular weight determination.
- Amino acid and carbohydrate composition analysis.
- N-terminal sequencing.
Main Results:
- Purified glycoproteins with Mr 43,000 (brain) and 45,000 (spleen).
- Similar amino acid compositions but differing carbohydrate content and glycosylation patterns.
- Broad tissue distribution confirmed by N-terminal sequencing.
Conclusions:
- The novel molecule is a glycoprotein with tissue-specific glycosylation.
- Its presence on diverse cell types suggests a broad functional role.
- Further research is needed to elucidate its precise function in T-cell regulation.