Immunophenotypic difference of keratin expression in normal mammary glandular cells from five different species

The immunohistochemical reactivity of human, monkey, shrew, rat and mouse normal mammary glands was examined using methacarn-fixed paraffin-embedded specimens and acetone-fixed frozen sections using the avidinbiotin-peroxidase method for cell phenotype comparison. Actin was visualized using anti-smooth muscle actin antibody and keratin expression was determined by employing 12 different monoclonal antibodies. All these antibodies cross-reacted specifically with the species examined. Basal (myoepithelial) cells from all species showed muscle-specific actin according to reactivity with HHF35 monoclonal antibody. Keratin expression showed significant phenotypic differences among species. In human and monkey, AEL-KS2, KL1, CK8.13, AE3 and 34BE12 stained luminal cells as well as basal cells. AE1, RPN1165, CK4.62, 35BE11, M20 and RPN1162 labeled only luminal cells whereas 312C8-1 preferentially bound to basal cells. In shrews, AEL-KS2, CK8.13 and AE3 reacted to both cell types, AE1 reacted only with luminal cells, and 35BE12 and 312C8-1 selectively stained basal cells. In rodents, AEL-KS2 reacted to both cell types, CK8.13, AE3, 34BE12 and 312C8-1 stained rat basal cells, and 34BE12 and 312C8-1 reacted to mouse basal cells. The data represents cytoskeletal differences among species.