Interferon-stimulated Ttp expression limits induction of TNFα and IL-6. (A) BMMs derived from Ttp wild-type (TTPWT) and deficient (TTPKO) mice were left untreated or treated with IFN-γ (g), LPS (L), or both (L/g) for 3 hours and TNFα mRNA induction was determined by qRT-PCR and normalized to untreated samples. * P < .05 treated versus untreated cells by univariate linear regression models. (B) BMMs from TTPWT and TTPKO were stimulated for the times indicated with IFN-γ (G), LPS, or both (L/G), or left untreated (0). Supernatants were collected and analyzed for TNFα cytokine by ELISA. *P < .01, 4 hours versus 2 hours in L/G-treated KO cells; †P < .01, KO versus WT BMMs by univariate linear regression models, n = 3 experiments.(C) TTPWT BMMs were treated for 30 minutes (30′) with IFN-γ and LPS, and activation of p38 was demonstrated using an antibody against phosphorylated p38 MAPK (pp38). Equal protein loading was confirmed using a p38 antibody. (D) BMMs from TTPWT and TTPKO mice were treated as described in panel A. Absence of TTP protein in TTPKO cells was confirmed by Western blotting of whole-cell extracts using a TTP antibody. Activation of IFN signaling by endogenous production of type I interferon in LPS-treated macrophages was demonstrated using an antibody to tyrosine-phosphorylated STAT1 (pY701-S1). Equal protein loading was confirmed using a STAT1 antibody and a panERK antibody. (E) BMMs from TTPWT and TTPKO were stimulated for the times indicated with IFN-β (B), LPS, or both (L/B) or left untreated(0). Supernatants were collected and IL-6 was measured by ELISA. *P < .01, 6 hours versus 4 hours in L/B-treated KO cells; †P < .01, KO versus WT BMMs by univariate linear regression models, n = 3 experiments.