Transgenic UCH-L1 synergizes with deregulated BCL6 in the development of B-cell lymphoma. (A) Representative histology of lymphomas observed in Uchl1^Tg/IμHABCL6 mice. Formalin-fixed paraffin-embedded sections were stained with hematoxylin and eosin (top 2 rows) or immunohistochemistry (bottom row) with antibodies against the indicated antigens. Bar: 1000 μm (top row), 100 μm (middle row), 400 μm (bottom row), 100 μm (inset, bottom row). Microscopy images were obtained with an Olympus AX70 microscope with a DP71 camera. (B) The incidence of lymphomas is shown for the indicated mouse strains. *P < .05 as determined with the χ² test; N = 29 mice for each genotype. (C-D) Immunoblots were performed on extracts from lymphomas as in panel A. Comparison is made with purified B cells (C), purified GCBs (D) from the spleens of wild-type littermates, or the indicated GCB-DLBCL cell lines (D). (E) Genomic DNA was extracted from the indicated samples and subjected to PCR amplification of immunoglobulin variable regions. The arrows denote unique monoclonal bands not seen in the polyclonal B cells.