Characterization of a crossreactive idiotype in Sjögren's syndrome.

Sjögren's syndrome (SS) is characterized by lymphoid infiltration of the salivary glands and autoantibody production. Rheumatoid factor (RF) in patients with primary SS (1 degree SS) contains a crossreactive idiotype (CRI) defined by a monoclonal antibody (MoAb 17-109). This CRI was located on the kappa light chain by immunoblotting methods. A high frequency of CRI+ B cells was found in SS salivary gland biopsies, suggesting this tissue as the site of production for this autoantibody. Further characterization of CRI+ RF from SS patients was performed using antibodies prepared against synthetic peptides corresponding to the hypervariable region of RF paraproteins from patients with Waldenström's macroglobulinemia (WM). These results demonstrate a close structural relationship between RF in SS and WM patients. To analyze the genes that encode these RF in SS patients, B cell hybridomas that secreted CRI+ immunoglobulin were created and their DNA analyzed by Southern blot techniques. These hybridomas will allow us to determine the DNA sequence of kappa genes encoding the CRI and to identify adjacent regulatory genes that may promote high levels of CRI expression.