Consistent with normal B220 expression, intracellular Pax5 staining revealed that the B‐ALL tumors of Cd79a‐Cre Ikzf1neo/+Pax5LSL‐Jak2/+ mice expressed high Pax5 levels similar to the wild‐type B cells (Fig 3H). This evidence concerns the gene PAX5 and acute lymphoblastic leukemia.