Interleukin-6 expression in response to innate immune regulatory factor stimulation.

Innate immune regulatory factor (IIRF) is a serum-derived biological response modifier, or agent that modifies/bolsters the pathogenic immune response. IIRF has been shown to provide protection (e.g., increase host survival) against a variety of pathogenic challenges including Salmonella typhimurium and Pasteurella multocida. In this report, we analyzed cytokine production in mice, whole blood and cultured cells in response to IIRF challenge. When IIRF was administered to mice, it stimulated the release of pro-inflammatory cytokines. Both IL-6 and IL-10 were temporally stimulated when IIRF was introduced. Serum IL-6 peaked at 3h (3957pg/ml) before returning to baseline by 8h, while IL-10 began to appear at 3h, peaked at 8h (734.5pg/ml), and returned to baseline by 36h. IIRF challenge also increased the expression of two positive acute phase proteins: haptoglobin increased 61-fold, while serum amyloid A levels increased ∼3500-fold in mice. A whole blood immunoassay indicated the effect of IIRF on production of IL-6 was dose- and time-dependent. Anti-asialo GM 1.1 provided to partially (>95%) eliminate functional natural killer cells elevated IL-6 in whole blood. IIRF was also able to induce the production of IL-6 in cultured human monocytic THP-1 cells. Based upon this study and previously reported data, we propose that IIRF activates the innate immune response via induction of IL-6 production.

The roles of translation initiation regulation in ultraviolet light-induced apoptosis.

Ultraviolet light (UV) inhibits translation initiation through activation of kinases that phosphorylate the alpha-subunit of eukaryotic initiation factor 2 (eIF2alpha). Two eIF2alpha kinases, PERK and GCN2, are known to phosphorylate the Serine-51 of eIF2alpha in response to UV-irradiation. In this report, we present evidence that phosphorylation of eIF2alpha plays a role in UV-induced apoptosis. Our data show that wild-type mouse embryo fibroblasts (MEF(s/s)) are less sensitive to UV-induced apoptosis than MEF(A/A) cells in which the phosphorylation site, Ser51, of eIF2alpha is replaced with a non-phosphorylatable Ala (Ser51Ala). PARP expression in MEF(A/A) cells is reduced without being cleaved after UV-irradiation. In contrast, PARP is cleaved without a significant decrease in parental PARP in MEF(S/S) cells after UV-irradiation. Our data also show that MEF(GCN2-/-) cells, in which GCN2 is knocked out, are more sensitive to UV-irradiation, agreeing with the observation from MEF(A/A) cells. However, MEF(PERK-/-) cells, in which PERK is knocked out, are less sensitive to UV-irradiation. In addition, MCF-7-PERKDeltaC cells, which are stably transfected with a kinase domain deleted mutant of PERK (PERKDeltaC), are more resistant to UV-induced apoptosis than parental MCF-7 cells. Overexpression of wild-type PERK sensitizes MCF-7 cells to UV-induced apoptosis without directly inducing cell death. These results suggest that the level of eIF2alpha phosphorylation impacts PARP expression upon UV-irradiation. The eIF2alpha kinases may mediate UV-induced apoptosis via an eIF2alpha dependent or independent signaling pathway.

Reducing mortality in Salmonella enterica serovar Typhimurium-infected mice with a tripeptidic serum fraction.

Salmonellosis-induced mortality in female Swiss Webster mice decreased significantly when tripeptidic immunostimulant (TPI) was administered prophylactically. Prophylactic benefits developed in a dose-dependent manner wherein 15 mg of TPI given 1 day before challenge reduced mortality by 70%.