[Clonal B-cell reactions and prelymphoma in autoimmune diseases]

With the establishment of the MALT concept in immunology it became obvious that B cells play an important role in the autoimmune diseases of the MALT. We immunophenotyped the intraepithelial B cells occurring in Hashimoto's disease, Sjögren's syndrome and Helicobacter pylori-associated gastritis and looked for clonal T-cell receptor gamma chains (TCR-gamma) and immunoglobulin heavy chains (JH). Immunophenotypically, we identified predominantly monocytoid B cells as the effector cells in the salivary glands of patients with Sjögren's syndrome, whereas in the thyroid and stomach the effector cells were marginal zone cells. Polyclonal rearrangements were found in 11/25 patients with Sjögren's syndrome, 23/40 patients with Hashimoto's disease and 19/24 patients with gastritis. Accordingly, 14 of the patients with Sjögren's syndrome, 17 of the patients with Hashimoto's disease and 5 of the patients with gastritis showed monoclonal rearrangements. Immunohistochemically, all patients with clonal rearrangements were found to have lymphoepithelial lesions. In these patients a transition to a low grade MALT lymphoma could be diagnosed. From these results we can conclude that in these two autoimmune diseases clonal rearrangements must be considered at least potentially malignant and that intraepithelial B cells should probably be considered the promoters of autoimmune diseases and of the development of primary extranodal B-cell lymphomas.