Red cell autoantibodies characterized by competitive inhibition of iodine 125 Rh alloantibody binding and by immunoprecipitation of membrane proteins.

The relationship between determinants recognized by warm-type immunoglobulin G red cell autoantibodies and the Rh antigens was characterized by autoantibody competitive inhibition of iodine 125 Rh alloantibody binding and autoantibody immunoprecipitation of iodine 125 red blood cell membrane proteins. The majority of blood donor autoantibody recognized epitopes that are closely related to Rh antigens as determined by competitive inhibition studies. Eighteen of 20 (90%) autoantibodies inhibited anti-Rh(c) binding, 15 inhibited anti-Rh(E), 5 inhibited anti-Rh(D), and only 2 failed to inhibit any of the three Rh alloantibodies tested.

IgG red blood cell autoantibodies in autoimmune hemolytic anemia bind to epitopes on red blood cell membrane band 3 glycoprotein.

Red blood cell (RBC) autoantibodies from patients with IgG warm-type autoimmune hemolytic anemia were labeled with iodine 125 and their RBC binding behavior characterized. Epitope-bearing RBC membrane polypeptides were identified after autoantibody immunoprecipitation of labeled membranes and immunoblotting. Immunoaffinity isolation of labeled membrane proteins with 12 different IgG hemolytic autoantibodies with protein A-agarose revealed a major polypeptide at Mr 95 to 110 kd, which coelectrophoresed on sodium dodecylsulfate-polyacrylamide gel electrophoresis with a membrane component isolated with sheep IgG anti-band 3.

Nonhemolytic red cell autoantibodies consist of multiple immunoglobulin G populations directed against complex membrane epitopes.

Immunoglobulin G red cell autoantibodies obtained by elution from six normal blood donors with antiglobulin-positive test results were labeled with iodine 125 and characterized by adsorption studies with primate and human red cells of common and rare Rh phenotype. Adsorbable IgG was determined by exhaustive adsorption with one type of red cell and by cross-adsorption with use of two different types of red cells. All of the labeled autoantibodies studied contained multiple populations directed against epitopes variably expressed on the different types of red cells (both rare and common phenotypes) used for adsorption.

Characterization of the D, c, E and G antigens of the Rh blood group system with human monoclonal antibodies.

The human MAbs, anti-D, -c, -E and -G of the Rh blood group system, produced by Epstein-Barr virus transformed B-cell lines, were purified by protein A-Sepharose chromatography and used to characterize the Rh antigens of human red cells. Scatchard plot analyses performed with the radiolabelled MABs indicated that each R2R2 red cell carries 0.43, 0.