Russell M W, Mansa B
Department of Oral Biology, Royal Dental College, Aarhus, Denmark.
Scand J Immunol. 1989 Aug;30(2):175-83. doi: 10.1111/j.1365-3083.1989.tb01199.x.
The complement-fixing properties of human IgA antibodies bound to specific antigen, or coated directly on plastic surfaces, were examined in comparison with those of IgG antibodies. Use was made of antigen-binding (anti-staphylococcal alpha-toxin) IgA and IgG monoclonal antibodies and normal polyclonal IgA and IgG, purified greater than 99.9% by avoidance of denaturing processes. Complement-fixation ELISA was used, with a high density of biotin-conjugated staphylococcal alpha-toxin bound to avidin-coated plates for the efficient capture of antibodies, and conditions were adjusted for the assessment of classical and alternative pathways of complement activation. Although IgA coated directly on plastic surfaces activated the alternative complement pathway in a dose-dependent manner, IgA antibodies bound to antigen failed to fix complement by either classical or alternative pathways. In contrast, IgG antibodies, either bound to antigen or coated directly on plastic, activated complement mainly by the classical pathway. It was concluded that the complexation of IgA antibodies with antigen is insufficient to elicit complement activation: rather a degree of denaturation seems to play a part in the expression of alternative complement pathway-activating properties by IgA.
将与特定抗原结合或直接包被在塑料表面的人IgA抗体的补体结合特性与IgG抗体进行了比较。使用了抗原结合性（抗葡萄球菌α毒素）IgA和IgG单克隆抗体以及正常多克隆IgA和IgG，通过避免变性过程纯化至大于99.9%。采用补体结合ELISA法，将高密度生物素偶联的葡萄球菌α毒素结合到抗生物素蛋白包被的板上以有效捕获抗体，并调整条件以评估补体激活的经典途径和替代途径。虽然直接包被在塑料表面的IgA以剂量依赖方式激活替代补体途径，但与抗原结合的IgA抗体不能通过经典途径或替代途径固定补体。相比之下，与抗原结合或直接包被在塑料上的IgG抗体主要通过经典途径激活补体。得出的结论是，IgA抗体与抗原的复合不足以引发补体激活：相反，一定程度的变性似乎在IgA替代补体途径激活特性的表达中起作用。
