title: Divalent cation effects on the binding of human anti-phospholipid antibodies.
abstract: Anti-phospholipid antibodies from sera of subjects with documented syphilis were measured as a result of their individual interactions with cardiolipin, phosphatidylserine and phosphatidic acid, each impregnated in nitrocellulose paper from chloroform solution, followed by reaction with a labelled second antibody. Binding curves generated by increasing the cardiolipin concentration over a standard area of nitrocellulose paper showed saturation. The presence of Ca2+ or Mg2+ during the antibody binding step resulted in a complex pattern of binding as a function of the cation concentration. When the extent of binding was normalized to percent of maximum bound, virtually super-impossible patterns were seen with different sera. These patterns were distinctive for both the phospholipid and the cation. The speculation is presented, albeit without any direct evidence, that the extent of antibody binding is sensitive to a variety of intermediate phospholipid phase structures which may be initiated by the presence of the specific divalent cation at a particular concentration.
mesh_terms: D001323:Autoantibodies; D002118:Calcium / Q000494:pharmacology*; D002413:Cations, Divalent; D006801:Humans; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology*; D010743:Phospholipids / Q000276:immunology*; D012016:Reference Values; D013587:Syphilis / Q000276:immunology*
chemical_list: D001323:Autoantibodies; D002413:Cations, Divalent; D010743:Phospholipids; D008274:Magnesium; D002118:Calcium