The aim of this study was to determine the degree to which
the epidermis and oral epithelium of species
other than man express cytokeratin (CK) intermediate filaments, which are
markers of epithelial
differentiation. Fixed, wax-embedded samples of skin, buccal
mucosa and gingiva from rhesus monkey,
marmoset, cow, sheep, pig, ferret, hamster, axolotl and trout
were tested for CK expression using a panel of
antihuman CK antibodies and an immunoperoxidase procedure. Human skin and
oral mucosa 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 profile. 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 evidence of variable anti-CK
antibody cross-reactivity, both as a result of intrinsic
variations in CK polypeptide structure and as artifacts
of fixation. We conclude that some CK are conserved between
species, but that biological variables, for
example local functional requirements, and technical factors
affect the results. These considerations need to
be borne in mind in animal studies of epithelial differentiation
employing CK immunohistochemistry.
Biochemical characterisation is ultimately necessary to determine
specific differences between human and animal CK.