A transgenic non-human animal, such as a mouse, has a genome that includes anucleic acid construct having at least one transcriptional regulatory sequencecapable ofdirecting expression in B cells of the animal, wherein the transcriptionalregulatory sequenceis operably linked to a nucleic acid encoding a miR155 gene product. A methodof testingthe therapeutic efficacy of an agent in treating or preventing alymphoproliferative conditionincludes assessing the effect(s) of the agent on a transgenic non-humananimal.
