immunology and infection of the gut: Flashcards
what is the microbiota in our gut?
- 10^4 resident bacteria. - Exposure to external pathogens - 4 major phyla: Bacteroidetes, Firmicutes, Actinobacteria and Proteobacteria.
what are the main fucntions of the microbiota?
- Oral tolerance. - Enzyme alteration. - Motility alteration. - Alteration of cell turnover
what is dysbiosis?
- altered microbiota composition
what might dysbiosis be caused by?
- infection - diet - xenobiotics - hygiene - genetics
what are the 3 areas to look at in mucosal defence?
- Physical defence - commensal bacteria - immunological
what is the immunological defence of the mucosal defence?
MALT and GALT.
where is MALT found?
oral cavity
where is GALT present? what are the two main forms?
GALT is rich in BOWEL. organised : - Cryptopatches - Peyer’s patches – small intestine - Isolated lymphoid follicles – colon. - Mesenteric lymph nodes. non organised: just floating randomly in subepithelial: - Intra-epithelial lymphocytes. - Lamina propria lymphocytes.
where are the peyers patches found?
- Found in the small intestine - Composed of B and T cell areas - Develops throughout life into teens
what are features of peyers patches?
-No goblet cells. - No secretory IgA. - No microvilli. - Infiltrated by T/B-cells, macrophages and DCs
how are antigens uptaken by the peyers patch?
- the m cells
what do dendritic cells do?
Dendritic cells sample antigen using dendrites
where do dendritic cells present the antigens?
- Naïve T-cells in Peyer’s patch. -Transport to mesenteric lymph nodes.
what happens in the peyers patches?
- Mature naïve B-cells express IgM in PPs. - Upon activation, class switch to IgA. - They populate the lamina propria
what secretes IgA ?
Up to 90% of the gut B-cells produce IgA
what is T cell homing?
The homing system is regulated by: o The T-cell exhibits a4b7-Integrin. o The gut epithelium exhibits MAdCAM-1. The receptor interaction means the t-cell is specific to the gut.
go over the cholera infectious diarrhea roataviruses noroviruses curved bacteria e coli Clostridium difficile
from the slides
what is the mechanism of Coeliac disease ?
- gluten is not broken down in the stomach - when it reaches the small intestine it binds to the sig A and is transferred to the lamina propria
what are symptoms of Coeliac disease?
Abdominal distension (bloating) Diarrhoea
what is diagnosis and treatment of Coeliac disease?
Ab blood tests - anti-gliadin. Biopsy test of duodenum - manage diet
what is the mechanism, symptoms and treatment of IBS?
- Visceral hypersensitivity - Recurrent abdominal pain Abnormal bowel motility Constipation and/or Diarrhoea - Diet modification - treatment of symptoms
what are the phases of inflammatory bowel disease?
- pre disease - acute intestinal inflammation - becomes chronic - tissue destruction fibrosis or even cancer
what are the initiating factors?
- genetic factors - environmental factors
***** differences between crohns and ulcerative colitis?
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