A high incidence of rheumatoid factor idiotypes in monoclonal proteins in the serum and in lymphoma cells in patients with Sjögren's syndrome.

Patients with Sjögren's syndrome (SS) develop lymphoproliferative disorders such as monoclonal gammopathies and non-Hodgkin's lymphomas. Cross-reactive idiotypes (CRI) were studied in 22 serum monoclonal immunoglobulins (Igs) and in cytoplasmic Ig in four B-cell lymphoma cells in patients with SS. This was done by utilizing monoclonal anti-idiotypic antibodies which were produced against monoclonal rheumatoid factors (RF) derived from three patients with SS and one patient with Waldenström's macroglobulinemia. By the Western blotting or dot immunobinding technique, CRI was detected not only in monoclonal RFs but in monoclonal Igs which had different heavy- or light-chains from the original monoclonal RF used for immunization. A higher incidence of CRI was found in 22 monoclonal Igs associated with SS than in 27 monoclonal Igs in patients with Waldenström's macroglobulinemia, multiple myeloma or malignant lymphoma. In four patients with malignant lymphoma associated with SS, three showed one or three CRI in the lymphoma cells, whereas only two out of 20 patients with other malignant lymphoma showed CRI, demonstrating a significant difference between two groups. These data indicate that monoclonal proliferation of B-cell lineage in patients with SS, benign or malignant, takes place more often among RF-producing clones than other B-cell disorders.