AITL-like pathology in Roquin^san/san mice. (A-B) Roquin^san/san mice develop generalized lymphadenopathy (A) and splenomegaly compared with Roquin^+/+ littermate controls (B). Lymph node sections were stained with hematoxylin and eosin (C-F) or antibodies to the macrophage marker F4/80 (G), B-cell marker pax-5 (H), or the pan-T-cell marker CD3ϵ (I-J). Enlarged lymph nodes are characterized by a polymorphic infiltrate containing plasma cells (E), macrophages (F-G), and atypical T cells sometimes forming a rosetta pattern characteristic of AITL (J). Pictures are representative of 4 mice analyzed, all 26 to 40 weeks of age.