Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.17 (lysozyme)
 21,489 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Brucella abortus injected into CBA mice replicated primarily in the spleen and liver, reaching a peak bacterial count in both organs about 7 days postinfection. The organism was eliminated from the liver but declined to a chronic phase in the spleen. The infection caused hepatosplenomegaly. An influx of macrophages into the two organs was monitored by quantitative Northern (RNA blot) analysis of the macrophage-specific marker lysozyme mRNA. Lysozyme mRNA was detectable in spleen and increased three- to fourfold during infection. In liver, lysozyme mRNA was initially undetectable, but at about the peak of infection it reached a level comparable to that in the spleen. Macrophage colony-stimulating factor 1 (CSF-1) has been reported to be elevated in the circulation of animals infected with B. abortus and is known to stimulate monocytopoiesis. To investigate the role of CSF-1 in pathogenesis, we studied the effect of further increasing the CSF-1 concentration by administration of recombinant human CSF-1. Since the infection is characterized by several distinct phases, recombinant human CSF-1 was administered at defined times relative to these phases. Pronounced effects were observed only when CSF-1 administration was begun during the developing acute phase. The consequences were decreased bacterial numbers in the spleen but an increase in the liver, reduced antibody generation, and increased hepatosplenomegaly. A feature of many chronic intracellular infections is immunosuppression. B. abortus caused a substantial diminution of responsiveness of spleen cells to T-cell mitogens, particularly concanavalin A. This action was mimicked by CSF-1 treatment of the animals prior to spleen cell isolation. The results suggest that CSF-1 plays a role in macrophage recruitment in brucellosis and that recruited macrophages contribute to the immunopathology and immunosuppression.
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PMID:Effect of recombinant human macrophage colony-stimulating factor 1 on immunopathology of experimental brucellosis in mice. 154 70

The radiative quantum yield, phi op, of the triplet state of human alpha-lactalbumin (HLA) has been measured in the temperature range between 6 K and the softening point of the aqueous glass (approximately 150 K). phi op has little temperature dependence below approximately 30 K, but above this it decreases sharply with increasing temperature. The unusual temperature dependence is fitted by a phenomenological two-state model in which the phosphorescence originates primarily from a donor, tryptophan (Trp) 104, and an acceptor, Trp 60, the populations of which are coupled by a thermally activated triplet-triplet energy transfer process. The model assumes that the acceptor (Trp 60) triplet state undergoes radiationless deactivation by a proximal disulfide residue, while the donor (Trp 104) has no such extrinsic quencher. The decrease of phi op with increasing temperature is accounted for by the thermally activated triplet-triplet energy transfer process. The disulfide quenching rate constant itself is assumed to be temperature independent, in accord with recent measurements of simple disulfide quenching in long chain snake venom neurotoxins (Schlyer, B. D., E. Lau, and A. H. Maki. 1992. Biochemistry. 31:4375-4383; Li, Z., A. Bruce, and W. C. Galley. 1992. Biophys. J. 61:1364-1371). We find that the phosphorescence quenching in HLA occurs with an activation energy of 97 cm-1, which we associate with a barrier to the energy transfer process. The data are fit well by the model if we assume a value for the temperature-independent disulfide quenching constant of kQ > 3 s-1 that is consistent with recent measurements on indole-disulfide model systems (Li, Z., A. Bruce, and W. C. Galley. 1992. Biophys. J. 61:1364-1371). Similar results are reported for bovine alpha-lactalbumin (BLA) and for hen egg-white lysozyme (HEWL) that contains the structural equivalents of Trp 104 and Trp 60 of HLA. HLA provides the best agreement with calculations since it is the simplest, lacking Trp 26, a residue not considered in the model, that probably contributes significantly to the phosphorescence of BLA, guinea pig alpha-lactalbumin (GPLA), and HEWL. GPLA, which contains Trp 104 but lacks Trp 60, shows qualitatively less thermally induced phosphorescence quenching than HLA, BLA, and HEWL, thus supporting the postulated quenching model.
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PMID:Temperature dependence of the phosphorescence quantum yield of various alpha-lactalbumins and of hen egg-white lysozyme. 836 13

Macrophages play a central role in host immune responses against pathogens by acting as both professional phagocytic cells and as fully competent APCs. We report here that the LPS from the facultative intracellular Gram-negative bacteria Brucella abortus interferes with the MHC class II Ag presentation pathway. LPS inhibits the capacity of macrophages to present hen egg lysozyme (HEL) antigenic peptides to specific CD4(+) T cells but not those of OVA to specific CD8(+) T cells. This defect was neither related to a decrease of MHC class II surface expression nor to a deficient uptake or processing of HEL. In addition, B. abortus LPS did not prevent the formation of SDS-resistant MHC class II complexes induced by HEL peptides. At the cell surface of macrophages, we observed the presence of LPS macrodomains highly enriched in MHC class II molecules, which may be responsible for the significant down-regulation of CD4(+) T cell activation. This phenomenon may account for the avoidance of the immune system by certain bacterial pathogens and may explain the immunosuppression observed in individuals with chronic brucellosis.
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PMID:Brucella abortus lipopolysaccharide in murine peritoneal macrophages acts as a down-regulator of T cell activation. 1104 53