Ectopic Pax5 expression results in immature T-cell lymphomas. (A) Immunophenotype of lymphoma cells. The spleen, thymus, and bone marrow of a wild-type (+/+) and 2 IgH^P5ki/P5ki (ki/ki) tumor mice were analyzed for CD4 and CD8 expression; TCRβ, CD19, CD25, and GFP expression is also shown for the splenocytes. (B) Clonal TCRβ rearrangements in Pax5-induced T-cell lymphomas. D_β2-J_β2 rearrangements were analyzed by PCR amplification of tumor DNA isolated from the thymus (T), lymph node (L), or spleen (S) of IgH^P5ki/+ and IgH^P5ki/P5ki mice. The different tumor mice are indicated by their numbers. The designations 7-10 and 7-13 refer to secondary lymphomas in the spleen of the recipient mice 10 and 13, which were intravenously injected with lymphoma cells from the spleen or thymus of tumor mouse 7, respectively. C indicates control tail DNA. Numbers to the right refer to the different J_β2 segments and GL to the germline PCR product.