HE-stained sections of the thymus (A) and spleen (B) of a transgenic mouse (Tg) and a nontransgenic control (C) (4 weeks of age). The boxed areas in the top panels are magnified in the bottom panels. (A) Thymus. In the lower magnification (top panels), transgenic thymus shows enlargement of the medulla and obscurity and irregularity of the medulla/cortex junction. In the higher magnification (bottom panels), the medulla of the transgenic thymus contains fewer thymocytes and consists of epithelial and interdigitating cells. Infiltrated neutrophils and multi-nucleated giant cells are indicated by black and white triangles, respectively, and the tingeble-body macrophages are indicated by an arrow. (B) Spleen. In the lower magnification (top panels), transgenic spleen shows marked disorganization in the fundamental structures. In the higher magnification (bottom panels), in a white pulp of the transgenic spleen, lymphocytes are markedly reduced and proliferation of neutrophils and megakaryocytes is observed. The central splenic artery, which is located in the middle of the white pulp, is indicated by an arrow.