Infection and immunology Flashcards
What is restrained activation of the gut? WHy must this occur?
Where the gut is primed to react to pathogens
- Due to massive antigen load because of high surface area and high microbiota
- It is both tolerance and immunoreactivity
What is the role of the microbiota?
Development of the immune system components
Provide traits that we have not needed to evolve ourself
- function as virtual organ
- provide ability to digest and metabolise
Why might bacterial populations vary in the GI?
DIfferent conditions
- some too hostile - stomach’s low pH
What are the types of microbiota?
Symbionts
- help us and provide nutrients
Commensal
- prevent adherence of pathogens to eptihelial wall
Pathogens
- cause inflammation
What is dysbiosis? What might cause this?
Imbalance of microbiota
Diet Antibiotics Infection Hygiene Genetics
What are the effects of dysbiosis?
Systemic diseases
Brain, lung and liver disorders
Outline the types of mucosal defence
Physical
- anatomical and chemical
Commensal bacteria
- prevent joining
Immunological - post-invasion
- MALT and GALT
Epithelial
- Paneth cells for lysozyme production
- Tight junctions
- mucous layer
What is MALT?
Mucosa associated lymphoid tissue
- lymphoid mass containing lymphoid follicles
Follicles are surrounded by HEV venules
What is GALT? HOw does it provide production? What are the two forms?
Innate immunity and adaptive response
Non-organised
- intra-epthelial, has T cells, NK cells
Organised
- Peyer’s patch -small intestine
- Caecal patch -large intestine
- Isolated lymphoid follicle
- Mesenteric lymph nodes
What are Peyer’s patches? Describe the organisation and brief composition
Immune sensors
Aggregated with lymphoid follicles
- follicle associated epithelium
- cant make IgA
- no goblet cells and little microvilli
Organised collection of naive T cells and B cells
Decelopment requires exposure to bacteria
Antigen uptake by M cells M cells express IgA receptors - facilitates transfer of IgA complex Also by dendritic cells - sample - doesnt compromise the tight junction
Is IgA dimeric of monomeric in the gut?
Dimeric as it is a SECRETORY form of IgA
how many mucosal layers does the large intestine have?
2 - Outer and inner
Outer is thicker - rich in lymphocytes
Outline lymphocyte honing and circulation from secondary lymphoid tissue, such as GALT and Peyer’s patches
Release to meet AG to activate
If no meeting, it returns
It will roam until it meets
What is MAdCAM-1?
An integrin, responsible for activation and honing of lymphocytes, back to the gut
What is the mechanism for choelra infection?
VIbrio cholerae reach small intestine
Close contact with epithelia leads to cholera toxin release
Cholera toxin enters cell, starting cascade that leads to ion exit
