FIGURE 4. TNBS-sensitized lymphocytes exacerbate colitis. Extent of mucosal inflammation was graded and mean total histologic scores per group (donor–acceptor) are shown. (A and B) NaCl–NaCl mouse (A) and TNBS–NaCl mouse (B) with normal colon architecture and small number of leukocytes in mucosa. (C) NaCl–TNBS mouse with inflammation (significantly less severe than in D), consisting of edema and influx of inflammatory cells, but no ulcerations and fibrosis. (D) TNBS–TNBS mouse with severe colitis characterized by edema, extensive influx of inflammatory cells, ulcerations, crypt loss, and fibrosis. (Hematoxylin–eosin, x33)