Langone J J, Das C, Bennett D, Terman D S
J Immunol Methods. 1983 Oct 14;63(2):145-57. doi: 10.1016/0022-1759(83)90419-2.
Radioimmunoassays have been developed that can detect nanogram amounts of protein A (SpA), a product generated by Staphylococcus aureus that binds selectively to the Fc region of IgG from most mammalian species. Competition assays for fluid phase SpA utilize antibodies produced in chickens, 125I-labeled SpA as the tracer molecule, and either F(ab')2 fragments of rabbit IgG anti-chicken IgG or 40% ammonium sulfate as the precipitating agent to separate antigen-antibody complexes from free antigen. The double antibody assay could be carried out in serum from species that form only soluble complexes with SpA (e.g., rabbit), that react poorly with SpA (e.g., rat), or under appropriate conditions in serum from species (e.g., dog) that show high reactivity with SpA and form precipitating complexes. Chicken antibodies prepared by affinity chromatography on SpA-Sepharose and labeled with 125I were used in a direct binding assay for SpA present either on the cell wall of Cowan strain I or Wood 46 bacteria, in insoluble complexes prepared from SpA and whole serum or purified IgG, or in Clq binding complexes that were formed by passage of serum from normal or tumor bearing humans or dogs over SpA-collodion charcoal. Since both types of assays could detect SpA even in the presence of serum or IgG, they offer advantages over other techniques in which the SpA-Fc interaction may interfere.
已经开发出放射免疫测定法，该方法能够检测到纳克量的蛋白A（SpA），蛋白A是金黄色葡萄球菌产生的一种产物，它能选择性地结合大多数哺乳动物物种IgG的Fc区域。液相SpA的竞争测定法利用鸡产生的抗体、125I标记的SpA作为示踪分子，以及兔抗鸡IgG的F(ab')2片段或40%硫酸铵作为沉淀剂，以将抗原-抗体复合物与游离抗原分离。双抗体测定法可在仅与SpA形成可溶性复合物的物种（如兔）的血清中进行，这些物种与SpA反应较差（如大鼠），或者在适当条件下，在与SpA反应性高并形成沉淀复合物的物种（如狗）的血清中进行。通过在SpA-琼脂糖凝胶上进行亲和层析制备并用125I标记的鸡抗体，用于对存在于考恩I株或伍德46株细菌细胞壁上的SpA、由SpA和全血清或纯化IgG制备的不溶性复合物，或由正常或荷瘤人或狗的血清通过SpA-胶态炭柱形成的Clq结合复合物中的SpA进行直接结合测定。由于这两种测定法即使在存在血清或IgG的情况下也能检测到SpA，因此它们比其他可能受到SpA-Fc相互作用干扰的技术具有优势。
