In terms of cell phenotype, PCL12 cells display a typical CLL cell phenotype: CD19+CD20+CD5+CD23+IgMlowIgDlow, in clear contrast to the MEC1 and MEC2 cells that express high levels of IgM and IgD and do not express CD5. The gene discussed is CD40LG; the disease is B-cell chronic lymphocytic leukemia.