Cytokeratin immunoreactivity in mouse tissues: Study of different antibodies with a new detection system

The cross-reactivity of a group of monoclonal antibodies (MaBs) generated a gainst human cytokeratins (CKs) was investigated in mouse tissues. Formalin -fixed and paraffin embedded sections of lung, stomach, small and large int estine, liver, and kidney were immunostained with MABs after epitope retrie val with enzyme digestion. AE1/AE3, a "cocktail" of two MABs that recognize s basic and acidic CKs, 5D3 MAB to low molecular weight CKs (8, 18, and 19) , and monospecific MABs to CK 7 and 20 were tested. Additionally, CK 17 and 34-beta E12 MABs to high molecular weight CKs were evaluated in the same o rgans and in sections from skin and preputial glands. We employed the new u niversal animal system (ARK) as the detection system. The results showed in tense reactivity for the first group of antibodies used, with topographic d istribution similar to that in human tissues, with the exception of CK 7 in lung parenchyma, which displayed reactivity only in type II pneumocytes, w ith negativity of adjacent bronchial epithelium. Also of note was the lack of reaction of Liver hepatocytes and renal tubular cells to AE I IAE3 and 5 D3 MABs. Regarding the second group of antibodies, no reaction was obtained for CK 17 in the tissues tested. On the contrary, 34 beta E12 MAB yielded intense reactivity in cells of epidermis and hair follicles. Compared to ot her detection systems used previously in this animal, ARK produced a well-d efined reactivity at the cellular level without any background. We conclude that a useful panel of anti-CK antibodies commonly used in human pathology can be applied successfully to mouse tissues after enzyme digestion, leadi ng to a more accurate definition of cellular populations in this laboratory animal.