CD19 and lymphoma: Compared with Eμ-Myc;CD19-Cre control lymphomas, BCL-2 protein expression was comparable in the Eμ-Myc;CD19-Cre;Mcl-1fl/+ lymphomas or, curiously, was lower in the Eμ-Myc;CD19-Cre;Mcl-1fl/fl lymphomas that had retained their Mcl-1fl alleles (Figure 2a).