Further immunohistochemical study of crooke's hyaline change.

In a previous study, we immunohistochemically investigated Crooke's hyaline change and concluded that it was composed of cytokeratin. The present study was undertaken to further identify the cytokeratin subfamily by immunohistochemistry. Twenty-eight postmortem, routinely processed pituitary glands revealing unequivocal Crooke's hyaline change were selected. To demonstrate Crooke's cellsand cytokeratin subfamilies simultaneously, serial hori zontal sections were sliced. Using an avidin-biotin peroxidase complex method, one was stained with a monoclonal antibody against synthesized adrenocorticotropic hormone (ACTH) 1-24, and the adjacent ones were stained with one of eight test monoclonal antibodies against cytokeratin subfamilies (containing cytokeratins 1, 3, 7, 8, 13, 18, and 19, and one containing 1,5, 10, and 11, respectively). A different antibody for each type of cytokeratin was applied. Crooke's cells showed a variable intensity of cytoplasmic stainingfor antibodiesagainst cytokeratins 8 and 18 (molecular weight 52.5 and 45 kD, respectively), from focal to more even and intense staining, revealing a characteristic wide brown ring around the nucleus or under the plasmalemma. The most severely affected cells were totally replaced by dark brown reaction products with no secretory granules detectable in the cytoplasm. However, Crooke's cells did not react with other test anticytokeratin antibodies. Thus far, it can be concluded that Crooke's hyaline change was composed of low-molecular-weight cytokeratin subfamilies 8 and 18, which are found in pairs in normal ACTH cells.