title: 125I protein A: applications to the quantitative determination of fluid phase and cell-bound IgG.
abstract: An improved method for the preparation of 125I-labelled Protein A (125I PA) of high specific and functional activity is described. 125I PA has been used in combination with purified rabbit IgG bound to a solid support to develop a competitive binding assay capable of detecting Protein A or human, rabbit and guinea pig IgG at the nanogram level. An optimal set of assay conditions was established and levels of IgG measured in normal human, rabbit and strain-2 guinea pig serum. 125I PA has also been used to detect IgG anti-Forssman antibody bound to sheep erythrocytes and to line-1 and line-10 tumor cells and as an indirect assay for tumor associated antigen in the ascitic fluid of tumor-bearing guinea pigs.
mesh_terms: D000818:Animals; D000906:Antibodies / Q000302:isolation & purification; D000951:Antigens, Neoplasm; D001667:Binding, Competitive; D004912:Erythrocytes / Q000276:immunology; D005577:Forssman Antigen; D006168:Guinea Pigs; D006801:Humans; D007118:Immunoassay; D007074:Immunoglobulin G; D007457:Iodine Radioisotopes; D009374:Neoplasms, Experimental / Q000276:immunology; D011485:Protein Binding; D011817:Rabbits; D012756:Sheep; D012995:Solubility; D013205:Staphylococcal Protein A / Q000276:immunology* / Q000378:metabolism
chemical_list: D000906:Antibodies; D000951:Antigens, Neoplasm; D007074:Immunoglobulin G; D007457:Iodine Radioisotopes; D013205:Staphylococcal Protein A; D005577:Forssman Antigen