Serological antibody ELISAs are useful to evaluate humoral immune response. Especially, in autoimmune disease patients and animal models, the assays allow to identify or detect autoantigens which may cause the disease.
However, there are still problems which many researchers do not recognize in the assays. ELISA plates were developed for not only indirect ELISAs but also sandwich ELISAs. The sandwich ELISAs use capture antibodies on the plate. The ELISA plates have been developed for its high hydrophobic binding capacity to adhese Fc section of IgG. It works well for the sandwich ELISA, however, in indirect ELISA, coexisting IgG in the serum samples also tend to attach on the plates nonspecifically. The binding is detected as antibody binding to an antigen on the plate, resulting in overestimated values. Especially, many autoimmune disease patients have sticky IgG in serum, which show higher IgG non-specific binding.
We have to choose appropriate buffers to prevent the IgG binding, or use antigen-uncoated plates to subtract the IgG binding from antigen-antibody reaction(1).