title: Cross-reactivity between C-reactive protein and idiotypic determinants on A phosphocholine-binding murine myeloma protein.
abstract: Binding of human 125I-C-reactive protein (CRP) to sheep erythrocytes sensitized with pneumococcal C polysaccharide (E-PnC) was found to be Ca++ dependent and inhibitable by phosphocholine, CRP, and HOPC 8. Binding of 125I-HOPC 8 to EPnC was Ca++ -independent but could also be inhibited by phosphocholine, CRP, and HOPC 8. Thus, CRP and HOPC 8, despite a differential Ca++ requirement, share a common binding specificity for phosphocholine. A monoclonal anti-idiotypic antibody (MAB), GB4-10, prepared in A/J mice immunized with BALB/c HOPC 8 inhibited the binding of both 125I-CRP and 125I-HOPC 8 to E-PnC. In addition, both proteins bound to GB4-10 immobilized on polysterene tubes. Interestingly, binding of 125I-CRP to GB4-10 required Ca++. Similar results were also obtained with another MAB (AB1-2) prepared similarly to GB4-10, whereas neither protein bound to a control MAB (EB3-7) against an alpha1 leads to 3 dextran-binding myeloma protein, J558. Binding of 125I-HOPC 8 to GB4-10 could be inhibited by HOPC 8, keyhole limpet hemocyanin-phosphocholine but not phosphocholine but not phosphocholine, and in the presence of Ca++ by CRP. These data indicate that CRP bears antigenic determinants cross-reacting with certain idiotypic determinants on HOPC 8. They also suggest that Ca++ acts as an allosteric effector, perhaps stabilizing the phosphocholine-binding site of CRP.
mesh_terms: D000818:Animals; D000918:Antibody Specificity; D001665:Binding Sites; D002097:C-Reactive Protein / Q000276:immunology*; D002794:Choline / Q000031:analogs & derivatives*; D002999:Clone Cells / Q000276:immunology; D003429:Cross Reactions; D000939:Epitopes; D007074:Immunoglobulin G / Q000276:immunology; D007130:Immunoglobulin Idiotypes; D051379:Mice; D009194:Myeloma Proteins / Q000276:immunology*; D010767:Phosphorylcholine / Q000276:immunology*
chemical_list: D000939:Epitopes; D007074:Immunoglobulin G; D007130:Immunoglobulin Idiotypes; D009194:Myeloma Proteins; D010767:Phosphorylcholine; D002097:C-Reactive Protein; D002794:Choline