Interleukin‐12 is required for interferon‐γ production and lethality in lipopolysaccharide‐induced shock in mice

Abstract

Several cytokines, in particular tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma), have been shown to be responsible for pathological reactions which may lead to shock and death observed in infection with Gram-negative bacteria and in response to endotoxins (lipopolysaccharides, LPS). Priming of mice with the avirulent Bacille Calmette Guérin (BCG) vaccine strain of Mycobacterium bovis increases the sensitivity of mice to the lethal effect of LPS and results in an efficient priming for cytokine production. In response to low doses (1 microgram/mouse) of LPS, BCG-primed mice produce interleukin-12 (IL-12) which controls IFN-gamma production, as demonstrated by the ability of neutralizing anti-IL-12 antibodies to suppress IFN-gamma production. However, the concentration of the biologically active IL-12 p70 heterodimer is similar in the serum of both BCG-primed or unprimed mice, reaching levels of 1-3 ng/ml at 3-6 h after LPS injection, whereas IFN-gamma production was observed only in BCG-primed mice. The priming effect of BCG on IFN-gamma production appears to be mostly due to its ability to increase TNF-alpha production, which acts as cofactor with LPS-induced IL-12 in inducing IFN-gamma production, as shown by the ability of injection of TNF-alpha and LPS (1 microgram/mouse), but not LPS alone, to induce IFN-gamma production. However, in addition to TNF-alpha, other LPS-induced cofactor(s) are required in cooperation with IL-12 to induce optimal IFN-gamma production, because co-injection of TNF-alpha and IL-12, sufficient to induce serum concentrations of both cytokines higher and more persistent than those obtained by injection of LPS, was not sufficient to induce IFN-gamma production in vivo. Neutralizing anti-IL-12 antibodies, in addition to inhibiting the in vivo LPS-induced IFN-gamma production, also completely protect BCG-primed mice injected with up to 10 micrograms of LPS from shock-induced death. Thus, IL-12 is required for IFN-gamma production and lethality in an endotoxic shock model in mice.

Induction of long-lasting cytokine effect by injection of IL-12 encoding plasmid DNA

“…Moreover, IFN -production was boosted after the second IL -12 DNA injection. Interestingly, in accordance to IL -12 synthesis, the rise of IFN -production showed a protracted rise reaching peak serum levels several days after the second IL -12 DNA administration, which may be explained by the ability of IL-12 to mediate both acute induction of the IFN -gene subsiding within 12 hours in vivo 31 and stable priming for high production of IFN -. Furthermore, this delayed response, which was also observed after application of recombinant IL-12 protein, 52 may be attributed in part to the lack of appropriate costimulatory signals (TNF -, IL-1 , B7, CD58 ) provided to some extent by APCs.…”

“…This long -term antimetastatic effect of IL-12 DNA therapy raises hope for its clinical use in adjuvant and palliative cancer and metastasis immunotherapy. It is in contrast to the shortlived recombinant IL -12 protein with a half -life of about 3.5 hours in mice (mu -IL12 ) 31 and between 5 and 10 hours in humans (hu -IL -12) . 32 The antimetastatic efficiency of IL-12 DNA therapy is linked to a pattern of long -term IL -12 expression with respect to duration and variability.…”

“…or subcutaneously in phase I and phase II clinical trials showing antitumor efficiency against advanced malignant melanoma and renal cell carcinoma. 27 ± 30 Limitations of this therapy were the short half -life of this protein 31,32 combined with high peaks of IL -12 serum concentrations generating serious toxicity. Side effects included fever, chills, fatigue, nausea, headache, anemia, neutropenia, lymphopenia, thrombocytopenia, hypoalbuminemia, hyperglycemia, triglyceridemia, liver function test abnormalities, and oral stomatitis.…”

Interleukin 12 Levels During the Initial Phase of Septic Shock With Purpura in Children: Relation to Severity of Disease

“…8 IL-12 also induces the production of interferon (IFN)-g by T cells and natural killer (NK)-cells. 16, 17 The plasma levels of IFN-g are increased in experimental models for sepsis [18][19][20] as well as in human sepsis, 21,22 although not consistently. 1 Recently, IL-12 was characterized as a major cytokine in the pathogenesis of gram-negative endotoxaemia in mice 16 and in primates.…”

In case of obesity, longevity-related mechanisms lead to anti-inflammation

“…Co-expression of both subunits is required to form the biologically active, secreted p70 heterodimer (Gubler et al 1991). IL-12 p40 is produced in much greater quantities than is required to form heterodimers (Wysocka et al 1995).…”