TSLP inhibits DC production of IL-12/23p40 in vivo and in vitro. (A and B) TSLPR^−/− mice have increased DC-derived proinflammatory cytokine production at day 10 after infection. Cells were isolated from MLNs and restimulated directly ex vivo with Trichuris ES antigen. Cells are gated on CD11c⁺ CD11b⁺ populations (A, TNF-α; B, IL-12/23p40). (C) IL-12/23p40 mRNA expression in the colon at day 12 after infection. Results represent means ± SEM. N, naive, uninfected control. Inf, infected day 12. (D–F) IEC-Sup specifically inhibit LPS-induced IL-12/23p40 production. (D) LPS-induced up-regulation of MHC class II, CD80, and CD86. (E and F) BMDC cytokine production was measured using intracellular cytokine staining (E, TNF-α; F, IL-12/23p40). (G and H) Cytokine secretion was assayed by ELISA of the supernatants (G, TNF-α; H, IL-12/23p40). Med, media + LPS; Sup, IEC-Sup + LPS. (I–K) rTSLP specifically inhibits LPS-induced IL-12/23p40 production. (I) LPS-induced up-regulation of MHC class II, CD80, and CD86. (J and K) BMDC cytokine production as measured using intracellular cytokine staining (J, TNF-α; K, IL-12/23p40). (L) IEC and rTSLP conditioning of BMDCs decreased CD4⁺ T cell production of IFN-γ upon co-culture. Percentages are shown in A, B, E, F, and J–L. Data in A–C represent two individual experiments with three mice per group. Data in D–K represent three to five individual experiments, and data in L represent two individual experiments. Shaded histograms in D and I indicate control, unstimulated BMDCs.