INTERSPECIES VARIATIONS IN ORAL EPITHELIAL CYTOKERATIN EXPRESSION

The aim of this study was to determine the degree to which the epiderm is and oral epithelium of species other than man express cytokeratin ( CK) intermediate filaments, which are markers of epithelial differenti ation. Fixed, wax-embedded samples of skin, buccal mucosa and gingiva from rhesus monkey, marmoset, cow, sheep, pig, ferret, hamster, axolot l and trout were tested for CK expression using a panel of antihuman C K antibodies and an immunoperoxidase procedure. Human skin and oral mu cosa were also stained to act as positive control. The results showed that antihuman CK antibodies stained animal tissues, but the patterns of staining were not always identical to the established human CK prof ile. Of particular interest was the expression of CK18, typically only detected in 'simple' epithelium in man, in bovine, ferret and hamster stratified epithelium from different sites. However, there was eviden ce of variable anti-CK antibody cross-reactivity, both as a result of intrinsic variations in CK polypeptide structure and as artifacts of f ixation. We conclude that some CK are conserved between species, but t hat biological variables, for example local functional requirements, a nd technical factors affect the results. These considerations need to be borne in mind in animal studies of epithelial differentiation emplo ying CK immunohistochemistry. Biochemical characterisation is ultimate ly necessary to determine specific differences between human and anima l CK.