Bacteria: Helpful and Harmful

1279 Words3 Pages

Gram negative bacteria such as Salmonella & E.coli, on the other hand, has lipopolysccharrides (LPS) as its main cell wall constituent activating TLR4.
Recognition of these MAMPS with a TLR by SIgA attaching to J-chain-containing Ig polymers and transepithelial transport via M, gives rise to induction of memory cells that change rapidly with the microbial environment (shown in Fig1) [9].
This is in contract to SIgA synergic responses of the immune system where systematic challenge changes memory cells in a slow process. This allows the gut environment to change without an inflammatory response when commensals and probiotics change the environment so that new bacteria can live symbiotically in [8]. Recognition via TLRs on dentricic cells causes signal cascades within the gut to induce cytokines, chemokines and antimicrobial factors (Fig 2). Commensal causes the nuclear factor B(NF-B) to inhibits NF-B kinase and MAPK via TLR4 attaching to lipossacharides on gram negative bacteria [10]. Signals allow for rapid post translational protein modifications. This prohibits tissue damaging immune responses to commensal bacteria and allows their survival and the death of pathogenic bacteria.
A loss in TLR signalling can cause inflammation when the epithelium is infected by pathogenic bacteria. Paneth cells are AMP secretary cells in the crypts of Lieberkuhn, which defend the host [8]. AMPs are the primary interactions with commensals and host cells within the innate immune response and directly kill pathogens and create a feedback loop (Fig3). In humans they are secreted into the blood and provoke defensin production. Ablation of MyD88 in Paneth cells reduces the synthesis of RegIII and creates defects in the epithelial barrier...

... middle of paper ...

...mmune Function, Infection and Inflammation: A review of the Evidence from Studies Conducted in Humans. Current Pharmaceutical Design. Vol 15. 1428-1518
8. Salzman, N. (2001). Microbiota- Immune System Interaction: an uneasy alliance. Current Opinion in Microbiology. Vol14. 99-105
9. Mizrahi, M & Ilan, Y. (2009) The gut mucosa as a site for induction of regulatory T-cells. Current Pharmaceutical Design. Vol 15 (11) 1191-1202
10. Faure,E. et al (2000). Bacterial Lipopolysaccharide Activates NF-κB through Toll-like Receptor 4 (TLR-4) in Cultured Human Dermal Endothelial Cells. The Journal of Biochemistry, 15, 11058-11063
11. Hörmannsperger, G. & Haller,D. (2010). Molecular crosstalk of probiotic bacteria with the intestinal immune system: Clinical relevance in the context of inflammatory bowel disease. International Journal of Medical Microbiology. Vol 300 (1) 63-73

Open Document