Abstract:

Objective To investigate the role of Castleman's disease in the pathogenesis of paraneoplastic pemphigus (PNP). Methods In six PNP patients associated with Castleman's disease, routine immunohistochemistry was performed on tumor tissue. Reverse transcription-PCR, DNA sequencing of cloned PCR product and in situ hybridization (ISH) were used to estimate the clonality of the B-cells in the tumors. The expression of the specific tumor B-cell clones was evaluated by Northern blot. Six patients with Castleman's disease without mucocutaneous lesion and 3 patients with reactive lymphadenopathy were used as the controls. Results Immunohistochemistry showed that CD20-positive B-cells in high density located in lymphoid follicles. The PCR produced one discrete band of about 128 bp in every paraneoplastic pemphigus patients. After sequencing the cloned PCR product, only two kinds of highly homologous sequences were found in all of the PNP patients. The 128 bp sequences were the major clones seen in all patients, and the 122 bp sequences were the relatively minor one seen in 4 patients. Anti-sense RNA probe transcribed from a clone of 128 bp was used in ISH. Signals of ISH located in cytoplasm of the cells in follicles of the tumors. Furthermore, this probe was also used for Northern blot and showed a strong signal in PNP patients. Conclusion Castleman's disease associated with PNP share a major B-cell clone. The B-cell clone is expressed and maybe produces functional antibody initiating the mucocutaneous immune injury.

Key words: Paraneoplastic pemphigus, Genes, immunoglobulin, Gene rearrangement