Characterization of the human erythrocyte complement receptor CR1 (C3b receptor) by epitope mapping.


Monoclonal antibodies and an anti-idiotypic serum against human complement receptor CR1 (C3b receptor, immune adherence receptor) were used to identify CR1 and some of its proteolytic fragments by an immunoblotting technique. The anti-idiotypic serum had a specificity for the C3b-binding site, as could be shown by its cross-reactivity with complement factor H. The monoclonal antibodies GARP-4 and GARP-37 were specific for epitopes located nearby the ligand-binding site, because they blocked the immune adherence reaction. For the immunoblotting technique, it was essential to use non-reducing conditions, since reduction of CR1 destroyed the epitopes. Therefore, mainly large (disulphide-linked) fragments of CR1 were obtained. A chymotryptic fragment of Mr 56,000 identified by GARP-4, was the smallest cleavage product to be associated with the C3b-binding domain. Different proteases gave CR1 degradation products of similar Mr, indicating the presence of distinct domains, three of which had a Mr approximately 38,000. A schematic model of CR1 substructure was deduced from the epitope mapping data.

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@article{Prohaska1987CharacterizationOT, title={Characterization of the human erythrocyte complement receptor CR1 (C3b receptor) by epitope mapping.}, author={Rainer Prohaska and Guenther R. Adolf}, journal={Immunobiology}, year={1987}, volume={174 1}, pages={93-106} }