Previous studies showed that local macrophages phagocytose nonantigenic chitin particles (1–10 μm polymers of N-acetyl-d-glucosamine) through mannose receptors and produce IL-12, IL-18, and TNF-α. These cytokines lead to the production of IFN-γ by NK cells. To determine whether chitin could down-regulate Th2 responses, chitin was given orally (8 mg/day for 3 days before and 13 days during ragweed allergen immunization) in BALB/c and C57BL/6 mice. These ragweed-immunized mice were given ragweed intratracheally on day 11. Three days after the challenge, the immunized mice with saline (controls) showed increases in serum IgE levels and lung eosinophil numbers. The chitin treatment resulted in decreases of these events in both strains. To dissect the inhibitory mechanisms of Th2 responses, spleen cells (4 × 106 cells/ml) isolated from the ragweed-immunized mice (controls) were cultured in the presence of ragweed and/or chitin for 3 days (recall responses). Ragweed alone stimulated the production of IL-4 (0.6 ng/ml), IL-5 (20 U/ml), and IL-10 (3.2 ng/ml), but not IFN-γ. Ragweed/chitin stimulation resulted in significant decreases of IL-4, IL-5, and IL-10 levels and the production of IFN-γ (48 U/ml). Moreover, spleen cells isolated from the chitin-treated mice showed ragweed-stimulated IFN-γ production (15 U/ml) and significantly lower levels of the Th2 cytokines, suggesting that the immune responses were redirected toward a Th1 response. Collectively, these results indicate that chitin-induced innate immune responses down-regulate Th2-facilitated IgE production and lung eosinophilia in the allergic mouse.

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Human intelectin-1 (hITLN-1) is a 120-kDa lectin recognizing galactofuranosyl residues found in cell walls of various microorganisms but not in mammalian tissues. Although mouse intelectin-1 (mITLN-1) has been identified previously, its biochemical properties and functional characteristics have not been studied. Therefore, we have compared structures and saccharide-binding specificities of hITLN-1 and mITLN-1 using recombinant proteins produced by mammalian cells. Recombinant hITLN-1 is a trimer, disulfide-linked through Cys-31 and Cys-48, and Nglycosylated at Asn-163. Despite 84.9% amino acid identity to hITLN-1, recombinant and intestinal mITLN-1 are unglycosylated 30-kDa monomers. Recombinant hITLN-1, as well as recombinant and intestinal mITLN-1 were purified by Ca 2+ -dependent adsorption to galactose-Sepharose. In competitive binding studies, hITLN-1 was eluted from galactose-Sepharose by 100 mM 2-deoxygalactose, a galactofuranosyl disaccharide, D-xylose, and both D-and L-ribose. In contrast, mITLN-1 was partially eluted by the galactofuranosyl disaccharide, and only minimally by the other saccharides indicating that the two intelectins have different saccharide-binding specificities. When the N-and Cterminal regions of hITLN-1 were replaced, respectively, with those of mITLN-1, galactose-Sepharose binding was associated with the C-terminal regions. Finally, hITLN-1 binding to galactose-Sepharose was not affected by the substitution of the Cys residues in the N-terminal region that are necessary for oligomer formation, nor was it affected by the removal of the N-linked oligosaccharide at Asn-163. Although both hITLN-1 and mITLN-1 recognize galactofuranosyl residues, our comparative studies, taken together, demonstrate that these intelectins have different quaternary structures and saccharide-binding specificities.

Intravenous (i.v.) administration of phagocytosable chitin particles (1 to 10 m) in C57BL/6 mice and SCID mice primed alveolar macrophages (M) within 3 days to yield up to a 50-fold increase in their oxidative burst when elicited in vitro with phorbol myristate acetate (PMA). C57BL/6 mice pretreated with monoclonal antibodies (MAbs) against mouse gamma interferon (IFN-␥) or NK1.1 showed a markedly decreased level of alveolar M priming following injection of chitin particles. To confirm IFN-␥ production in vitro, spleen cells isolated from normal C57BL/6 mice and SCID mice were cultured with chitin particles. Significant IFN-␥ production was observed following stimulation with chitin but not with chitosan or latex beads. When spleen cells were treated with anti-NK1.1 MAb, IFN-␥ production was significantly inhibited. Another set of experiments showed that when C57BL/6 mice were pretreated i.v. with a small dose IFN-␥, a higher level of priming was induced with not only phagocytosable chitin particles but also phagocytosable chitosan and even latex beads. Likewise, the spleen cell cultures preconditioned with IFN-␥ provided an up-regulation of IFN-␥ production by these phagocytosable particles. Taken together, the in vivo and in vitro results suggest that (i) the alveolar M priming mechanism is due, at least in part, to direct activation of M by IFN-␥, which is produced by NK1.1 ؉ CD4 ؊ cells; (ii) IFN-␥ would have an autocrine-like effect on M and make them more responsive to particle priming; and (iii) phagocytosis of particulates, probably by a postmembrane event such as interiorization, appears to be important for the up-regulation of alveolar M priming and IFN-␥ production.

The MBCs of nafcillin, vancomycin, gentamicin and daptomycin (LY146032) were determined for three clinical isolates of coagulase-negative staphylococci grown in suspension and adherent to biomaterials. Strains studied were the slime-producing strain Staphylococcus epidermidis RP-12 (ATCC 35983), S. hyicus SE-360, and the non-slime-producing strain S. hominis SP-2 (ATCC 35982). All three strains were allowed to colonize surgical-grade disks of stainless steel, polymethylmethacrylate, and ultrahigh-molecular-weight polyethylene for 24 h, and the disks were then exposed to various concentrations of antibiotics for 24 h. Surviving adherent bacteria were mechanically dislodged from the disks and quantitated by standard broth dilution plating techniques. Biomaterial-adherent RP-12 and SE-360 yielded approximately 10 times more CFU per disk than non-slime-producing SP-2 did. For all organisms, 10 times more bacteria bound to polymethylmethacrylate disks than to the other biomaterials. In general, bacteria adherent to biomaterials exhibited greater resistance to antibiotics than the same strains in suspension did. Resistance was independent of bacterial slime-producing characteristics and was related to the biomaterial colonized.Biomaterial-centered infections are characterized by the following features: (i) a biomaterial or damaged tissue substratum; (ii) adhesive, frequently polymicrobial bacterial colonization; (iii) persistence of infection until the substratum is removed; (iv) resistance to host defense mechanisms and antibiotic treatment; (v) specificity of materials, organisms, and location; and (vi) transformation of autochthonous or opportunistic organisms to virulent pathogens (18).Mechanisms of antibiotic resistance have not been well characterized. A biofilm barrier effect has been proposed (4,5,7,16,30). Studies have shown that when organisms are grown in suspension they are susceptible to lower concentrations of antibiotics than when they are in surface-adherent, biofilm-enclosed populations (4,5,16,20,24). The selection of therapeutic antibiotics is usually based on standard suspension culture MIC and MBC studies. In this study, antibiotic susceptibilities of organisms grown in suspension and on biomaterials were examined.The ability of antibiotics to kill coagulase-negative staphylococci is clinically important, since studies have shown that staphylococci are major colonizers of surgical biomaterials, including heart valves, intravascular catheters, and orthopedic appliances (la, 6). Prosthetic infections are generally resistant to antibiotic therapy and frequently require removal of the implant before eradication of the infection is possible (12-19).Both coagulase-positive and coagulase-negative staphylococci have been reported as causes of biomaterial-centered infections, with a tendency for coagulase-negative species to be associated with polymer-sited infections (2,12,15,26 (2,21). RP-12 is an adherent slime producer, whereas strain SP-2 has been reported to be nonadherent to smooth, inert surfaces a...

Treatment of mice with heat-killed (HK)Mycobacterium

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