By far the most relevant Cre-recombinase alleles for the design of BL, FL and DLBCL mouse models are the Cγ1-Cre and Aicda-Cre knock-in alleles, which allow for precise Cre-mediated gene recombination in antigen-activated mature B cells, including GC B cells (Figure 3A) (42–44). This evidence concerns the gene AICDA and diffuse large B-cell lymphoma.