Examples include IgM+ B cell lymphomas with lymphoplasmacytic features that developed in BALB/c mice deficient in Fas signaling (C.Lpr/Gld) [255, 256], strain NSF.V+ mice congenic for ecotropic murine leukemia virus (MuLV) [257, 258], and compound transgenic mice in which the Trp53-encoded tumor suppressor, p53, had been specifically inactivated in mature B cells [259] (Figure 6(b)). Here, CD40LG is linked to B-cell non-Hodgkin lymphoma.