title: A specific monoclonal antibody (PG-B6) detects expression of the BCL-6 protein in germinal center B cells.
abstract: The BCL-6 gene is frequently involved in translocations occurring at the 3q27 locus and is rearranged in approximately 30% of diffuse large cell lymphomas and in a small fraction of follicular lymphomas. The BCL-6 gene encodes for a Kruppel-type zinc-finger protein, the cell/tissue expression and function of which is unknown. In this study, we describe a new monoclonal antibody (PG-B6) that is specifically directed against a fixative-sensitive epitope on the amino-terminal region of the BCL-6 protein. By immunocytochemical analysis, BCL-6 localizes in the nucleus where PG-B6 staining gives a microgranular/diffuse pattern with exclusion of the nucleoli. The main reactivity of PG-B6 in tonsil and spleen is with the nuclei of germinal center B cells, whereas B cells within the mantle and marginal zones do not express BCL-6. No other lymphoid cells in the tonsil express BCL-6 except for a subset of CD3+/CD4+ intrafollicular and interfollicular T cells. A few lymphoid cells of unknown phenotype express BCL-6 in the thymus. Extra-lymphoid BCL-6 expression includes a weak nuclear positivity of epithelia. In non-Hodgkin's lymphomas, BCL-6 expression parallels that observed in normal lymphoid compartments, eg, expression in germinal center-derived tumors (follicular and diffuse large cell lymphomas), but not in mantle cell and marginal zone lymphomas. In most diffuse large cell lymphomas, the BCL-6 protein is expressed at high levels in cases with or without BCL-6 gene rearrangements. These findings indicate that BCL-6 expression is specifically regulated during B lymphocyte development and suggest that BCL-6 may play a role during B cell differentiation in the germinal center.
authors.affiliation: Institute of Internal Medicine, University of Perugia, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Flenghi
authors.forename: B H
authors.initials: BH
authors.lastname: Ye
authors.forename: M
authors.initials: M
authors.lastname: Fizzotti
authors.forename: B
authors.initials: B
authors.lastname: Bigerna
authors.forename: G
authors.initials: G
authors.lastname: Cattoretti
authors.forename: S
authors.initials: S
authors.lastname: Venturi
authors.forename: R
authors.initials: R
authors.lastname: Pacini
authors.forename: S
authors.initials: S
authors.lastname: Pileri
authors.forename: F
authors.initials: F
authors.lastname: Lo Coco
authors.forename: E
authors.initials: E
authors.lastname: Pescarmona
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology*; D000918:Antibody Specificity; D001402:B-Lymphocytes / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000276:immunology* / Q000378:metabolism*; D008221:Lymphoid Tissue / Q000166:cytology / Q000378:metabolism*; D016393:Lymphoma, B-Cell / Q000378:metabolism* / Q000473:pathology; D008228:Lymphoma, Non-Hodgkin / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D011518:Proto-Oncogene Proteins / Q000276:immunology* / Q000378:metabolism*; D051560:Proto-Oncogene Proteins c-bcl-6; D012016:Reference Values; D014157:Transcription Factors / Q000276:immunology* / Q000378:metabolism*
chemical_list: D000911:Antibodies, Monoclonal; D004268:DNA-Binding Proteins; D011518:Proto-Oncogene Proteins; D051560:Proto-Oncogene Proteins c-bcl-6; D014157:Transcription Factors