Low doses of HgCl2 induce a genetically restricted autoimmune syndrome in Brown Norway (BN) rats (BN(Hg)). Part of the syndrome includes spontaneously developing mononuclear cell foci in salivary and lacrimal glands, morphologically similar to focal sialoadenitis in Sjögren's syndrome in man. In this study, we have shown that Hg-induced focal adenitis in BN rat is not female predominant and not solely dependent on Hg uptake in the glands. In BN(Hg), focal adenitis was found to develop in several different glands (parotid, submandibular, lacrimal, thyroid) as a specific manifestation of immunopathosis induced by Hg in the RT1n-haplotype-carrying BN. Such manifestations were absent in another strain, the Hg-resistant Lewis (RT1l). Also a potent contact sensitizer, DNFB, induced focal adenitis in isolated glands, provided that strong sensitization had occurred. Immunohistochemical characterization of focal adenitis in BN(Hg) with monoclonal antibodies showed that T cells and dendritic cells dominate the early infiltrates, whereas B cells were absent.