Figure 2.

Immunohistochemistry with the monoclonal antibody specific for the 4-HNE–His shows the prominent presence of the protein adducts of the aldehyde in connective tissue (brown) below the 4-HNE–His negative epithelium (blue) of esophagus of a healthy rat (left photo 100×) and in the blood vessel (indicated by the yellow arrow). In human colon cancer, 4-HNE can be seen only in the nuclear region of a few cancer cells (right photo 50×). In both cases the presence of 4-HNE–protein adducts is visualized by dark brown di-amino-benzidine staining, with the blue hematoxylin contrast staining.