PAX5 and T-cell non-Hodgkin lymphoma: As ectopic Pax5 expression in the T‐lymphoid lineage leads to the development of an aggressive T cell lymphoma (Souabni et al, 2007), we used the Cd79a‐Cre line (Hobeika et al, 2006) to convert the Ikzf1neo to the Ikzf1Pax5 allele only at the onset of B cell development.