Flashcards in IMI5: Immune responses against extracellular pathogens Deck (121)
Main mediators of innate immunity are?
pattern recognition receptors
Where do 75% of immune cells reside?
mucosal immune system
The commensal flora are collectively known as?
The human microbiome
Bacteria can secrete antibiotics or antimicrobial peptides called ________ which can work as a first line defence against an invader
Give two examples of harmless bacteria that can become pathogenic
1) The infection by the commensal microorganism Staphylococcus epidermidis after a break in the skin from a cut
2) Pseudomonas aeruginosa, which most of us can fight effectively, can infect the airways, urinary tract and wounds of vulnerable individuals and cause real harm (e.g. by causing pneumonia and in some cases sepsis)
Name 3 life-threatening bacteria that grow in the respiratory tract
Streptococcus pneumoniae, Haemophilus influenzae, Bordetella pertussis
What can Streptococcus pneumoniae, Haemophilus influenzae, Bordetella pertussislead to?
blood stream infections (when viable bacteria or fungi are found circulating in blood), pneumonia, meningitis and middle ear infections
What are the two immunologically distinct regions of the gut?
Effector site (makes up most of gut)
What are the inductive sites
Regions rich with naive resting immune cells: . These regions drive the education of the immune system of mucosal surfaces
What are the regions responsible for education of the immune system of mucosal surfaces called?
What happens in Peyer's patches?
They sample microbes in the lumen of the gut, passing them on to macrophages and B cells to promote IgA responses against these pathogens. In contrast, dendritic cells (DCs) sample other antigens to ensure that immune cells are tolerant of food, and other gut contents that are not hazardous
Where is the effector site?
the tissue underlying the epithelium (embedded within the matrix of the peyer's patch)
What is the effector site made u of and what does it do?
It is crammed with activated effector cells: plasma cells that secrete antibodies into the mucus (usually IgA and IgM) and memory B cells, T helper (TH) cells and antigen presenting cells (APCs) - macrophages and dendritic cells.
lymphatics from peyer's patches and villi drain into where?
Mesenteric lymph node
What is the loose connective tissue within the villi called?
What cells transport material across epithelial barrier via transcytosis
Microfold cells (M cells)
What do dendritic cells within Peyer's patch do?
Extend dendrites between epithelial cells to sample antigens that are the broken down and then used for presenting to lymphocytes
What is tolerogenic activation?
Where the immune system initiates and anti-inflammatory response
With their cargo of antigen, what do the dendritic cells within the Peyer's patch do?
Traffic to the T-cells zones. Upon encounter with T-cells, the dendritic cells convert them into regulatory T cells
Defects in the function of what cells causes inflammatory bowel disease?
regulatory T cells
Where do the regulator T cells migrate to? How?
lamina propia of the villi via the lymphatics
What do regulatory T cells do whenever they get to the lamina propia?
Secrete IL-10, which exerts an supressive reaction with the immune cells of the lamina propia and on the epithelial layer itself
What interleukin is critical in maintaining immune quiescence and preventing unnecessary inflammation
A break down in immune homeostasis can lead to what?
gut pathology - over a log period and in an uncontrolled manner this can lead to
inflammatory bowel disease
What are the causes of inflammation in the gut?
- genetic predisposition plus
- chemical, mechanical or pathogenic barrier disruption
When bacteria influxes through the epithelium what do T-regulatory cells do? How are they activated to do this?
Down regulate IL-10 secretion, to allow an immune response to proceed.
They are activated by alarm molecules secreted by the epithelium following activation by bacteria
What is released by dendritic cells during a gut immune response?
IL-6, IL-12, IL-23
What do effector T cells do in the gut during an immune response?
They up-regulate the immune response by secreting: tumor necrosis factor, interferon gamma, IL-17
Following effector T cell arrival in the gut, what comes next?
- netosis (NET)
causes collateral damage to tissues