Low expression of hnRNPLL, as observed upon Pax5‐mediated repression in control B‐ALL and B cells, leads to the inclusion of all three exons in the Ptprc mRNA giving rise to the CD45 isoform RABC (known as B220), while increased expression of hnRNPLL, as detected in Pax5Jak2/+ B‐ALL cells, results in skipping of individual exons (Fig 2H), giving rise to other CD45 isoforms (Oberdoerffer et al, 2008), including RBC and RB (Appendix Fig S2I). This evidence concerns the gene PTPRC and acute lymphoblastic leukemia.