Absence of donor APC-derived IL-23 significantly attenuates proinflammatory cytokine production in the colon. (A,B) Lethally irradiated (900 cGy) Balb/c mice were transplanted with B6 BM (10 × 10⁶) and spleen cells (0.4-0.6 × 10⁶) (■) or IL-23^−/− BM (10 × 10⁶) and spleen cells (□) adjusted to yield an equivalent number of mature T cells. Cohorts of mice (7-9/group) were killed at the indicated time points (days 4, 7, 14, 21, and 28), and segments of colon tissue from individual mice were cultured overnight in media. Colonic tissue supernatants were collected and analyzed for the amount of IL-23p19 (A) and IL-12p70 (B) by ELISA and multiplex, respectively. Data are presented as mean amount of cytokine divided by the weight of cultured colon tissue (± SEM) and are cumulative results from 2 experiments. (C) Groups of mice were transplanted as in panels A and B and killed 28 days posttransplantation. Colons (n = 4-5/group per experiment) were pooled and digested with collagenase D. Total number of isolated LPMCs that were CD11c⁺ CD11b⁺ or CD11b⁺ CD11c⁻ in Balb/c recipients of B6 BM and spleen cells (■) or IL-23^−/− BM and spleen cells (□) is depicted. Data are derived from 3 independent experiments and are presented as the mean cell number (×1000) per mouse (± SEM) (D). Lethally irradiated Balb/c mice were transplanted with B6 BM plus spleen cells (n = 10, ■) or IL-23^−/− BM and spleen cells adjusted to yield equivalent numbers of T cells (n = 9, □). Mice were killed 21-29 days posttransplantation, and colon explant tissue was assayed for levels of proinflammatory cytokines by multiplex. Data are derived from cumulative results from 2 experiments and are presented as the mean amount of cytokine divided by the weight of cultured colon tissue (± SEM). Statistics: *P ≤ .05; **P < .01.