Trans-splicing is not likely the responsible mechanism for the generation of chimeric transcripts. Burkitt lymphoma cell lines (Ramos, DG75, CL-01, and BL2) cells, while expressing both BCL6 and germ-line IgM transcripts, do not express the chimeric Iμ-BCL6E2 or BCL6E1-Cμ1 transcripts. Tonsil no. 23 (T23) cells were included as a positive control. The results represent 3 independent experiments.