Ultrastructural observations on the parotitis autoimmunica in the NZB/NZW hybrid mice.

The lesions of the spontaneously occurring sialoadenitis in the parotid gland of New Zealand Black/New Zealand White (NZB/NZW) hybrid mice were studied with the light microscope and the electron microscope. The inflammatory mononuclear cell infiltrates of the glands observed adjacent to glandular vessels and ducts were found to consist of several different cell types. Lymphoid cells (large, medium sized and small lymphocytes) were the most common, but plasma cells, histiocytes and macrophages were also encountered. Furthermore lymphoid cells were frequently observed inside the basement membrane of acini as well as INTERcalated ducts. Evidence of cell damage of the epithelium invaded by lymphoid elements included loss of cytoplasmic density, vesiculation of the endoplasmic reticulum, the appearance of cytoplasmic vacuoles, and cellular lysis. All the animals studied displayed moderate to advanced glomerular, wire-loop lesions in the kidneys. The light and electron microscopic findings indicate that the parotitis in NZB/NZW mice is basically a vasculitis. Duct cell proliferation and epimyo-epithelial island formation, which are common features in Sjögren's syndrome, are totally lacking in the material studied.