Lecture 10 : microflora and mucosal immune system Flashcards
What are the** multiple physical barriers** in the GIT?
- saliva in the oral cavity - eg lyzozyme kills bacteria
- there are tight junctions in the epithelium of the GIT and these restrict diffusion of solutes etc
- HCL in the stomach
What is MALT?
- mucosa associated lymphoid tissue - the lymphoid tissue distributed in the mucosa
- eg appendix and peyers patches in the ileum
What is GALT?
- Gut associated lymphoid tissue
- lymphoid aggregates throughout the GIT
Describe are the **functions of microbes **in the GIT?
* protective functions - can produce antimicrobial factors & they compete with bacteria for nutrients / receptors
* **structural functions **- apical tightening of junctions - forms a barrier between cells & can tighten in response to harmful bacteria
* metabolic functions - synthesize vitamins & ion absorption
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how are microbes in the GIT distributed?
- Microbes are distributed across the GIT
- less in stomach due to HCL
- large density of bacteria in colon
what factors affect our microbial composition?
- the delivery procedure during birth - ie vaginal or c section
- whether baby is breast fed or bottle fed
- age
- antibiotics (deplete microbiota)
- lifestyle - ie active / exercise
what are examples of cell types in the mucosal immune system of the GIT?
- Lymphocytes
- macrophages
- dendritic cells
- neutrophils
- epithelial cells
- goblet cells
- paneth cells ( in crypt)
Describe lymphocytes
what are they, types, where do these types mature, where do they move to
- type of white blood cell found in the immune system
- they **include natural killer T cells and B cells **
- B cells mature in bone marrow & T cells mature in the thymus (organ in chest)
- they are concentrated in lymphoid organs and tissues / lymphoid aggregates eg peyers patches
What are the molecular differences between T and B lymphocytes?
- the helper T cells have a toll like receptor & CD4 protein
- the cytotoxic T cells have a toll like receptor & CD8 protein
- B lymphocytes contain B cell receptors
How does an undifferentiated T helper cell differentiate?
- by exposure to certain molecules
- eg undifferentiated T helper on exposure to IL-4 forms B cells
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What are macrophages?
type of white blood cell that engulf and digest pathogens via phagocytosis
what are denditic cells?
- a type of phagocyte that sends its long processes out through the tight junctions to collect the antigen and then presents it to other immune cells
What are neutrophils?
type of white blood cell that are the first responders to infection
What are phagocytes?
they are cells that protect the body by ingesting foreign particles eg bacteria
How do goblet cells contribute to the mucosal immune function?
they form a protective secretion that is composed of mucin and lysozyme
How do M cells work?
- M cells take up antigens from the gut lumen by endocytosis
- antigens are released beneath M cells and taken up by antigen presenting dendritic cells
