Although IgM+ lymphoproliferations and B lymphomas demonstrating lymphoplasmacytic features have been observed in laboratory mice in the past—for example, in C mice deficient in Fas signaling,46, 47 NSF.V+ mice congenic for an ecotropic murine leukemia virus48, 49 and mice in which the Trp53-encoded tumor suppressor, p53, had been specifically inactivated in mature B-cells50—none of these models mimic human WM as consistently as the BCL2+IL6+AID− model. Here, FAS is linked to lymphoma.