Toll-like receptors are activated by microorganism invasions via Myd88-dependent and/or -independent (Toll-IL-1 receptor domain-containing adaptor inducing interferon-β [TRIF]) signaling, which then triggers immune responses of the host. We have previously demonstrated that Myd88 deficiency blunted cytokine production in peritoneal macrophages (PMφ) taken from either sham, tissue injury (cecal ligation, CL) or septic (cecal ligation & puncture, CLP) mice. In splenocytes (Spl), Myd88 deficiency restored the Th1 cytokine response in CL and CLP mice. However, a significant aspect of Toll-receptor signaling is Myd88 independent, thus, we examined the effect of TRIF in sepsis. To study this, C57BL/6 (B6) or TRIF−/− mice were subjected to sham, CL or CLP. 24h later, plasma, PMφ, splenic Mφ (SMφ) and Spl were harvested and cultured with LPS or anti-CD3; cytokines were detected by cytometric bead array and/or ELISA. For survival study, B6 and TRIF−/− mice were subjected to CLP and followed for 10 days.TableThe results show that while serum levels of pro-inflammatory cytokines (TNFα, IL-6 and MCP1) were markedly increased after CL/CLP in both mouse strains, TRIF−/− mice exhibit reduced cytokine levels in CLP group. While cytokine release in LPS-stimulated PMφs was significantly decreased after CL/CLP compared to sham in B6 mice, TRIF deficiency showed a further blunting of these cytokines' release in all three groups. However, no such change was observed in SMφs or Th1/Th2 cytokine release in Spl. Furthermore, TRIF−/− mice exhibited an early improvement in survival (P < 0.05, n = 14-16/gp). Taken together, these data suggest that both Myd88 and TRIF signaling contribute to sepsis-induced inflammation. Although there are some similarities in the effect of innate immune response, they differ in the adaptive immune response. (NIH GM46354).