Immunoglobulin variable region gene rearrangement and hypermutation in paraneoplastic pemphigus associated Castleman's tumor
We have studied the role of lymphoproliferative tumors in the pathogenesis of autoimmune and the origin of the autoantibodies in paraneoplastic pemphigus (PNP) in recent years. A Castleman's tumor from a patient was identified to produce autoantibody. To identify the relationship between the tumor and pathogenesis of the disease, we analyzed the rearrangement of immunoglobulin variable region gene and its hypermutation in B cells of Castleman's tumor from a patient who was diagnosed of paraneoplastic pemphigus. The surface markers of cultured tumor lymphocytes were assessed with immunochemistry staining. After total RNA of the tumor cells were isolated, the mRNA was reversely transcribed into cDNA. V(H) and V(L) genes were cloned and their sequences were analyzed. Immunochemistry staining and flow cytometer analysis showed that the tumor cells were CD20, HLA-DR, smIgM, and smIgG positive. The cloned IgV(H) and IGHV3-9*01 germ-line gene are homologous and so are the Ig V(L) and the IGKV4-1*01 germ-line gene. More nucleotide changes in the V(H) or V(L) occurred in CDRs than those in FRs. In this reported case, a clone of specific B-lymphocyte in the Castleman's tumor carrying functional rearranged immunoglobulin heavy and light chain genes was found to have experienced switch recombination and was possible to produce IgG autoantibody.