Basket and basal-duct cells in domestic animals: different cytokeratin expression and shape

Cytokeratins (CKs) are a multigenic family of proteins constituting intermediate filaments in epithelia, indicated in humans by the numbers 1-20. Different cell-types can be immunocytochemically identified on the grounds of their CK expression. This investigation was designed to study CK expression of basket cells (BCs) and basal-duct cells (BDCs) in some domestic animals. Frozen sections of mammary and major salivary glands from cows, sheep, pigs and rabbits were treated using the immunofluorescent method, using as monoclonal antibodies clones CK-E3, CKB1, KS-1A3, and LDS-68, respectively, revealing the human CKs 17, 14, 13, 7. BCs surrounding acini and BDCs were stained by CK 17 antibody only in the rabbit. CK 14 was detectable in both cell types in cows, sheep and pigs, except in the case of bovine salivary BCs. CK 13 was revealed in BCs and BDCs of all mammary glands and also rabbit salivary glands. In the salivary glands of the other species, only BDCs were stained. CK 7 gave unreliable results in all the species and cell types examined. Interestingly, in the rabbit, also BDCs are basket-like in shape. The antibodies employed showed different staining depending on species and gland. On the grounds of immunoreactivity and shape, BCs and BDCs can be considered the same cell type in the rabbit. In the other species, they appear to be different, since BDCs may express additional CKs and are triangular-shaped, whereas BCs are truly basket-like. It is worth noting that clone KS-1A3 in the rabbit and CKB1 in the sheep and pig can be considered markers of the basket/ basal system.