AICDA and B-cell chronic lymphocytic leukemia: To further validate AID activity in TCL1 tumors, we performed mutation analysis of PCR-amplified IgM switch regions (Sμ region) by NGS-based sequence analysis of sorted CLL cells from primary TCL1, TCL1 Tx, primary TCL1-AIDKO, TCL1-AIDKO Tx (n = 3 each) and TCL1 multiple Tx (n = 2) samples (Figure 4A).