N of Phe and to lesser extent Trp thus producing equimolar amounts of an a-ketoacid (phenylpyruvate), H2O2 and NH3 [3]. The well-known toxic effect of H2O2 was potentiated by basification of the medium by NH3, demonstrating that the IL4I1 antibacterial effect does not buy IQ-1 simply rely on H2O2 production. Phe or Trp depletion might also participate to growth inhibition in bacterial strains auxotrophic for these amino acids. However, it did not appear to be a major mechanism of action in our in vitro experimental conditions, where no diminution of the Phe content could be evidenced. IL4I1 is 101043-37-2 produced by mononuclear phagocytes stimulated by bacterial products and pro-inflammatory cytokines, such as type I IFN, IFNc and TNFa [2]. In the context of bacterial infections, IL4I1 could be either secreted at the contact zone between the phagocytic cell and the bacteria, in the recently called “phagosomal synapse” [12] or released in the phagolysosome, in both cases contributing to the bactericidal arsenal of the macrophage. Several amino acid degrading enzymes, produced by myeloid cells in mammals, have been demonstrated to participate in antiinfectious effects together with an immunosuppressive activity directed towards T lymphocytes [13]. These enzymes sharea common mechanism of action: amino-acid depletion together with the production of a variety of toxic compounds, constituting a repertoire of weapons against a large spectrum of diverse microbial targets. The redundancy of this system may also suggest its importance for the host response. IL4I1 thus represents a new member of this complex and coordinated antimicrobial system. Addition of IL4I1 to bacteria injected in mice diminished the bacterial load in the spleen, concomitantly reducing the inflammatory response, independently of the previously demonstrated immunomodulatory effect of IL4I1. In humans, we previously reported a high level of IL4I1 production in macrophages associated with tuberculosis granuloma [2], suggesting a role for IL4I1 in both the containment of the bacterial dissemination and modulation of the Th1 cell response, in order to preserve the organ from the consequences of uncontrolled inflammation. Such a mechanism has also been proposed for the indoleamine 2,3 dioxygenase enzyme in the context of listeria granuloma [14]. IL4I1 is phylogenetically derived from bony fishes LAAO [7], some of which have been shown to use the enzyme to limit the growth of parasite larvae in structures resembling granuloma [9]. Thus, as it has been described for other aminoacid-catabolising enzymes [13], IL4I1 may have evolved from ancestral innate antimicrobial functions to acquire a regulatory effect on the adaptive immune system.Materials and Methods Cell Culture, Media and ReagentsMonocytic THP1 and Human embryonic kidney 293 (HEK) cell lines were cultivated respectively in RPMI 1640 and DMEMIL4I1 Antibacterial PropertiesFigure 6. IL4I1 inhibition of bacterial growth in vivo and associated plasmatic cytokine variations. (A) MSSA was added to HEK-PBS or IL4I1-PBS, and the mixes were injected intraperitoneally into groups of three C57Bl/6 mice (mean of 1.746108 CFU/mouse). Twenty-four hours after injection, supernatants from dissociated spleens were serially diluted and inoculated onto LB agar plates. Bacterial colonies were then counted. The ratio of the CFU in each mouse, relative to the mean CFU from triplicate HEK-PBS mice from each of the four experiments was calculated. Data are represen.N of Phe and to lesser extent Trp thus producing equimolar amounts of an a-ketoacid (phenylpyruvate), H2O2 and NH3 [3]. The well-known toxic effect of H2O2 was potentiated by basification of the medium by NH3, demonstrating that the IL4I1 antibacterial effect does not simply rely on H2O2 production. Phe or Trp depletion might also participate to growth inhibition in bacterial strains auxotrophic for these amino acids. However, it did not appear to be a major mechanism of action in our in vitro experimental conditions, where no diminution of the Phe content could be evidenced. IL4I1 is produced by mononuclear phagocytes stimulated by bacterial products and pro-inflammatory cytokines, such as type I IFN, IFNc and TNFa [2]. In the context of bacterial infections, IL4I1 could be either secreted at the contact zone between the phagocytic cell and the bacteria, in the recently called “phagosomal synapse” [12] or released in the phagolysosome, in both cases contributing to the bactericidal arsenal of the macrophage. Several amino acid degrading enzymes, produced by myeloid cells in mammals, have been demonstrated to participate in antiinfectious effects together with an immunosuppressive activity directed towards T lymphocytes [13]. These enzymes sharea common mechanism of action: amino-acid depletion together with the production of a variety of toxic compounds, constituting a repertoire of weapons against a large spectrum of diverse microbial targets. The redundancy of this system may also suggest its importance for the host response. IL4I1 thus represents a new member of this complex and coordinated antimicrobial system. Addition of IL4I1 to bacteria injected in mice diminished the bacterial load in the spleen, concomitantly reducing the inflammatory response, independently of the previously demonstrated immunomodulatory effect of IL4I1. In humans, we previously reported a high level of IL4I1 production in macrophages associated with tuberculosis granuloma [2], suggesting a role for IL4I1 in both the containment of the bacterial dissemination and modulation of the Th1 cell response, in order to preserve the organ from the consequences of uncontrolled inflammation. Such a mechanism has also been proposed for the indoleamine 2,3 dioxygenase enzyme in the context of listeria granuloma [14]. IL4I1 is phylogenetically derived from bony fishes LAAO [7], some of which have been shown to use the enzyme to limit the growth of parasite larvae in structures resembling granuloma [9]. Thus, as it has been described for other aminoacid-catabolising enzymes [13], IL4I1 may have evolved from ancestral innate antimicrobial functions to acquire a regulatory effect on the adaptive immune system.Materials and Methods Cell Culture, Media and ReagentsMonocytic THP1 and Human embryonic kidney 293 (HEK) cell lines were cultivated respectively in RPMI 1640 and DMEMIL4I1 Antibacterial PropertiesFigure 6. IL4I1 inhibition of bacterial growth in vivo and associated plasmatic cytokine variations. (A) MSSA was added to HEK-PBS or IL4I1-PBS, and the mixes were injected intraperitoneally into groups of three C57Bl/6 mice (mean of 1.746108 CFU/mouse). Twenty-four hours after injection, supernatants from dissociated spleens were serially diluted and inoculated onto LB agar plates. Bacterial colonies were then counted. The ratio of the CFU in each mouse, relative to the mean CFU from triplicate HEK-PBS mice from each of the four experiments was calculated. Data are represen.
