Autoantibodies are antibodies which react with self components, and occur not only in patients with autoimmune diseases but also in some normal subject, suggesting that autoantibodies may have some pathologic as well as physiologic roles. Recently, anti-idiotypic reagents were generated by immunization with synthetic peptides corresponding to the hypervariable regions of some human monoclonal anti-IgG antibodies (rheumatoid factors, RFs). These anti-idiotypes detected two """"""""primary structure-dependent"""""""" crossreactive idiotypes (CRIs) on 80% human monoclonal RFs, indicating that the majority of these RFs are encoded by single light chain variable region gene, designated Vk(RF). Indeed, the putative Vk gene was cloned from a normal human placenta and was found to be identical with four human RF light chains. Very recently, the cloned Vk(RF) gene was shown to used by a significant portion of RFs in most patients with Sjogren's syndrome (SS). Thus, using CRI positive RFs in SS patients as a model system, the overall objectives are to identify and characterize all Ig gene elements required for RF activities, to define the polymorphisms of these RF-related genes in human populations, to analyze the RF gene products and to delineate the molecular basic of RF production in SS patients and control normals. Specifically, (i) RF-secreting cell lines will be generated from SS patients with high titers of CRI+ RFs transformation with Epstein Barr virus and/or fusion with appropriate partners. Then, their specific rearranged heavy and light chain variable region genes will cloned and characterized. Subsequently, the corresponding germline gene segments will be identified and studied. (ii) B cell lines from SS patients and normals will be established to provide unlimited supply of genomic DNA, which will analyzed for restriction fragment length polymorphisms (RFLPs) of the RF-related genes. (iii) Sequence- specific antibodies will be induced with synthetic peptides corresponding to the characteristic regions of RF-genes, and will be applied characterize the RF-gene products in humans. Furthermore, plasmids will constructed to elucidate the cis- and trans-regulatory factors involved regulating expression of the RF-genes in SS patients.
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