Demonstration of substances of innate immunity in the esophageal epithelium of domesticated mammals. Part I - Methods and evaluation of comparative fixation

The aim of the investigation was to demonstrate that the esophageal epithelium of domesticated mammals exhibits characteristic features of innate immunity. The esophageal samples used were obtained immediately after euthanization from seven species of domesticated mammals of three nutrition groups (herbivores: horse, goat, cattle; omnivores: pig, dog, laboratory rat; carnivores: cat). The experimental basis was immunohistochemistry, which was evaluated in a qualitative and statistically relevant semi-quantitative manner. The first part of the study analyzed the influence of different fixation media on the immunohistochemical reactivities. Two formalin-based routine fixation solutions (Bouin's solution, Ca-acetate formalin) were compared with the recently introduced formalin-free HOPE® fixative. In this context, we clearly demonstrated a diminished immunoreactivity for Ca-formol fixed samples; satisfactory results were obtained, particularly, from samples fixed in Bouin's solution. The HOPE® fixation method offers a relatively cheap alternative, as the antibody amounts can be reduced. An application in routine diagnostic is not advisable, because of several variable parameters. It can be concluded that immunohistochemical results have always to be evaluated and discussed in close relation to the fixation medium used.