ETO and Bcl-6 are coexpressed in hematopoietic tissues and in normal and malignant B cells. (A) Human tissue cDNA obtained from Clontech (Palo Alto, CA) was used to detect ETO and Bcl-6 by PCR with primers designed to amplify ETO but not ETO-2 or MTGR1. RT-PCR with ETO-specific 3′ UTR primers is shown. (B) Normal human tonsils were submitted to immunohistochemistry for ETO. (Top) Extensive staining for ETO in germinal center and marginal zone lymphocytes (original magnification, × 10). (Middle) × 100 magnification of a section of the germinal center. (Bottom) Rabbit serum control staining (× 10) of tonsil. (C) mRNA was extracted from human FL, human DLBCL, and human normal tonsil and subjected to RT-PCR for ETO or Bcl-6 using primers specific for ETO but not ETO-2 or MTGR1. GAPDH RT-PCR and no-RT-GAPDH PCR reactions were also performed as positive and negative controls, respectively. RT-PCR with ETO-specific 3′ UTR primers is shown. (D) RT-PCR was performed on RNA extract from Raji and Daudi cells. RT-PCR for β actin and no-RT-β actin PCR reactions were also performed as positive and negative controls, respectively. The PCR products were run in 2% agarose gel. RT-PCR with the coding region (ORF) and the 3′UTR ETO-specific primers is shown. (E) Immunoblot of ETO and Bcl-6 was performed on lysates from Daudi and Raji cells with ETO and Bcl-6 polyclonal antibodies.