title: Interaction 125I-protein A with erythrocyte-bound IgG.
abstract: The molar combining ratio of 125I-PrA to RBC-bound 125I-labeled IgG anti-D was 0.72 +/- 0.044. There was a significant decrease in the PrA-to-IgG combining ratio when anti-D was bound to protease-modified RBCs or to unmodified RBCs sensitized at low ionic strength, 0.49 +/- 0.034 and 0.56 +/- 0.006, respectively. These findings indicate that the interaction of RBC-bound IgG with PrA may be influenced by alterations in membrane structure, surface density, and distribution of the IgG receptor and possibly other steric factors. The quantity of RBC-bound IgG on RBCs sensitized with unlabeled serum anti-D and anti-Kell could be quantitatively assessed and correlated with antiglobulin agglutinability. Unlabeled alloantibodies were detected with the 125I-PrA at IgG densities lower than those detectable with the standard antiglobulin test. 125I-PrA, in contrast to the antiglobulin reaction, has the potential of providing increased sensitivity as well as quantitative data in assessing IgG alloantibody- or autoantibody-sensitized RBCs. (J Lab Clin Med 99:399, 1982.)
mesh_terms: D000818:Animals; D004912:Erythrocytes / Q000378:metabolism*; D006041:Goats / Q000276:immunology; D007074:Immunoglobulin G / Q000378:metabolism*; D007457:Iodine Radioisotopes; D011485:Protein Binding; D011817:Rabbits / Q000276:immunology; D013205:Staphylococcal Protein A / Q000097:blood*
chemical_list: D007074:Immunoglobulin G; D007457:Iodine Radioisotopes; D013205:Staphylococcal Protein A