BD Retrievagen A (pH 6.0) is an antigen retrieval system that is recommended for Zinc-fixed and Formalin-fixed paraffin embedded tissue sections that show sub-optimal or no reactivity with antibodies for immunohistochemical staining. 10% neutral buffered formalin fixes the tissue by cross-linking proteins that may cause a conformational change or "masking" of the antigenic epitope leading to reduced or absent antibody reactivity. The BD Retrievagen A (pH 6.0) is designed to unmask the epitope and cause the enhancement of antibody staining. The proposed mechanism by which most of the antigen retrieval systems work is through breaking the cross-linking bonds formed between the protein molecules.
It is important to realize that in spite of antigen retrieval, some antibodies do not stain on formalin-fixed paraffin embedded sections. In these situations fixing the tissue in a less harsh fixative like the IHC zinc fixative developed by BD Pharmingen (Cat. No. 550523) may be helpful. In many cases our zinc-fixative preserves the epitope leading to good antibody staining at the same time depicting good tissue morphology. However, there are a few antigens that are not preserved by any gentle fixation, and in these situations use of fresh frozen tissue for immunohistochemical staining is the only alternative.