title: Downregulation of the B-cell receptor signaling component CD79b in plasma cell myeloma: a possible post transcriptional regulation.
abstract: The CD79 molecule, encoded by the CD79a and CD79b genes, is a signaling unit of the B-cell receptor complex, which transmits signals of B-cell activation, growth, and differentiation. They are B-cell-specific and expressed at most stages of B-cell development. Although plasma cells have been believed to lack these gene products, the regulation of CD79 expression in plasma cells is still controversial. In particular, the regulation of CD79b expression remains unclear. We sought to examine CD79b expression in normal and neoplastic plasma cells by immunohistochemical analysis. Out of the 23 clinical samples and 11 cell lines of plasma cell myeloma (PCM), none of the clinical samples and only 1 of 11 cell lines expressed CD79b immunohistologically, whereas non-neoplastic plasma cells in reactive hyperplastic lymph nodes exhibited loss of CD79b protein expression. This finding is quite different from our previous report on CD79a. Not only immunocytochemistry, but also RT-PCR and Western blot analysis of PCM cell lines gave identical results. Interestingly, we detected mRNA transcripts of CD79b in PCM cell lines, although protein translation was lacking. These findings suggest that expression of CD79b is downregulated in both plasma cells and plasma cell myeloma, and this process is possibly under post transcriptional regulation.
authors.affiliation: Department of Pathology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan.
authors.forename: Xingang
authors.initials: X
authors.lastname: Huang
authors.forename: Katsuyoshi
authors.initials: K
authors.lastname: Takata
authors.forename: Yasuharu
authors.initials: Y
authors.lastname: Sato
authors.forename: Takehiro
authors.initials: T
authors.lastname: Tanaka
authors.forename: Kouichi
authors.initials: K
authors.lastname: Ichimura
authors.forename: Maiko
authors.initials: M
authors.lastname: Tamura
authors.forename: Takashi
authors.initials: T
authors.lastname: Oka
authors.forename: Tadashi
authors.initials: T
authors.lastname: Yoshino
mesh_terms: D051925:CD79 Antigens / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D045744:Cell Line, Tumor; D015536:Down-Regulation; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007150:Immunohistochemistry; D008221:Lymphoid Tissue / Q000276:immunology / Q000378:metabolism; D009101:Multiple Myeloma / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D012333:RNA, Messenger / Q000378:metabolism; D011947:Receptors, Antigen, B-Cell / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D051925:CD79 Antigens; C497883:CD79B protein, human; D012333:RNA, Messenger; D011947:Receptors, Antigen, B-Cell