Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0519030 (Klebsiella)
 21,988 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The reaction of the intestinal immune system to intestinal bacteria shows striking differences between various bacterial strains. Whereas Klebsiella pneumoniae induces a fierce proinflammatory reaction, the probiotic strain Lactobacillus rhamnosus has clear anti-inflammatory effect in gastrointestinal disease and allergy. The molecular basis for this dichotomy is poorly understood but is likely to involve different modulation of antigen-presenting dendritic cells (DC) by L. rhamnosus and K. pneumoniae. Hence we evaluated phenotypic and functional characteristics of DC matured in the presence of L. rhamnosus and K. pneumoniae. Monocyte-derived immature DC were cultured in the presence of live bacteria to obtain mature DC. Both micro-organisms induced maturation of immature DC as shown by CD83 and CD86 expression, but receptors involved in activation of Th1 cells were expressed predominantly on DC exposed to K. pneumoniae. In contrast to K. pneumoniae, maturation with L. rhamnosus resulted in lower TNF-alpha, IL-6, and IL-8 production by immature DC and lower IL-12 and IL-18 production by mature DC. Moreover, L. rhamnosus led to the development of T cells without a typical Th phenotype whereas K. pneumoniae induced a Th1 immune response, dependent mainly on IL-12 production. Thus our results strongly support the concept that differential modulation of DC explains the differences in the immune response to various bacterial strains and indicates that K. pneumoniae induces Th1 immune responses via DC.
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PMID:Dichotomy between Lactobacillus rhamnosus and Klebsiella pneumoniae on dendritic cell phenotype and function. 1467 29

In humans, Klebsiella pneumoniae is a saprophytic bacterium of the nasopharyngeal and intestinal mucosae that is also frequently responsible for severe nosocomial infections. Two major factors of virulence, capsular polysaccharide (CPS) and lipopolysaccharide (LPS) O antigen, are involved in mucosal colonization and the development of infections. These bacterial surface structures are likely to play major roles in interactions with the mucosal immune system, which are orchestrated by a network of surveillance based on dendritic cells (DCs). To determine the roles of K. pneumoniae CPS and LPS in the DC response, we investigated the response of immature human monocyte-derived DCs to bacterial challenge with a wild-type strain and its isogenic mutants deficient in CPS or LPS O-antigen production. As observed by flow cytometry and confocal laser microscopy, the rate of phagocytosis was inversely proportional to the amount of CPS on the bacterial cell surface, with LPS playing little or no role. The K. pneumoniae wild-type strain induced DC maturation with upregulation of CD83, CD86, and TLR4 and downregulation of CD14 and DC-SIGN. With CPS mutants, we observed a greater decrease in DC-SIGN, suggesting a superior maturation of DCs. In addition, incubation of DCs with CPS mutants, and to a lesser extent with LPS mutants, resulted in significantly higher Th1 cytokine production. Combined, our findings suggest that K. pneumoniae CPS, by hampering bacterial binding and internalization, induces a defective immunological host response, including maturation of DCs and pro-Th1 cytokine production, whereas the LPS O antigen seems to be involved essentially in DC activation.
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PMID:Roles of capsule and lipopolysaccharide O antigen in interactions of human monocyte-derived dendritic cells and Klebsiella pneumoniae. 1984 Oct 82