Demonstration of fibronectin in normal and acutely inflamed appendix

The presence and localization of fibronectin in normal and acutely inflamed appendices in man was studied using indirect immunoperoxidase technique on sections of formaldehyde fixed and paraffin embedded tissue, following pretreatment with pepsin and testicular hyaluronidase. In the normal appendix fibronectin was demonstrated in the region of the basement membrane of the surface epithelium, in the loose connective tissue, in the perimysium around the individual smooth muscle cells and in the vessel walls. In the acutely inflamed appendices, fibronectin was found in the luminal necrotic area, both intercellularly and in the cytoplasma of some inflammatory cells. In relation to the surface inflammation and in the tissue matrix corresponding to the acute inflammatory reaction fibronection was, compared to the normal appendix, found in increased amount. Furthermore, a comparison between the use of a primary antibody to fibronectin, produced in our collaborating laboratory and two different commercial primary antibodies showed that the staining results concerning the localization of fibronectin were equal for all three antibodies, whereas the commercial antibodies showed a weaker staining intensity and some unspecific staining compared to the antibody produced in our collaborating laboratory.