Antibody cross-linking can occur when target antigen epitopes in the tissue sample are shared with other proteins that exist naturally in the tissue sample. This results in background staining. The most effective method of minimizing this type of non-specific staining is incubating the tissue section in a blocking serum before incubation in the primary antibody.
Blocking serums consist of dilute serum from the same species used to produce the secondary antibody. They are applied just before the incubation of the primary antibody. Blocking serums can be made of 1% to 20%, depending on the tissue and antibody used. Higher concentrations of blocking serums are used when the primary antibody has a high protein concentration. Blocking serums can also be added to buffer wash solutions, which is usually unnecessary for most IHC staining techniques.
