Lithium attenuates gut GVHD. (A-B) Lethally irradiated (1300 cGy) B6D2F1 recipients were transplanted with bone marrow (BM) (5 × 10⁶) with or without purified splenic T cells (3 × 10⁶). Recipients received a normal control or lithium-containing diet (0.2% from day −2 to +2 then 0.4% from day 3 onward). Semi-quantitative GVHD histopathology in (A) ileum (left) and colon (right) at day +7 after HSCT. (B) Representative hematoxylin and eosin images of ileum. (C-D) Wild-type B6 recipients were lethally irradiated (1000 cGy) and transplanted with BALB/c BM (10 × 10⁶) and purified splenic T cells (5 × 10⁶) with control or lithium diet treatment as described above. (C) Semiquantitative GVHD histopathology in ileum, colon, liver, and skin at day +7 after HSCT. (D) Representative hematoxylin and eosin images of ileum and colon. Scale bar, 100 μm. n = 3 to 10 per group. GI tract from 2 replicate experiments; liver and skin from 1 experiment. Data are presented as mean ± standard error of the mean (SEM). ∗∗P < .01; ∗∗∗∗P < .0001.