Animal with GVHD-like disease.

Small bowel from the animal that developed GVHD-like disease shows enterocyte denudation (arrows) and T cells (brown) infiltrating the lamina propria. (A) CD3 immunostain. (B-C) Close-up views immunostained for CD4 (B) and CD8 (C) show damage to basal crypts. Macroscopically, small bowel mucosa showed flat villi. All other organs sampled were infiltrated with T cells (both CD4 and CD8), including colon, kidneys, heart, skin, lungs, pancreas, and liver. In the liver, T cells infiltrated more the portal spaces than the parenchyma. In agreement with that, during IL-7 administration alkaline phosphatase peaked at 26 times above baseline, γ-glutamyltransferase 12 times above baseline, alanine aminotransferase 2 times above baseline, and bilirubin 3 times above baseline. The thymus was small, barely visible, at autopsy and microscopically contained few CD3⁺ cells (both CD4⁺ and CD8⁺); the corticomedullary junction was indistinct. Spleen and mesenteric LNs were moderately enlarged, whereas axillary and inguinal LNs were of normal size. No germinal centers were present; most cells in the spleen (both in the white and red pulp) and in the LNs were T cells (both CD4⁺ and CD8⁺); B cells (CD20⁺) were markedly decreased. Viral inclusions or syncytia were not seen in any of the organs sampled. Original magnifications, × 30 (A) and × 50 (B-C).