Inflammation Flashcards
What are the four cardinal features of inflammation?
Rubor - redness
Calor - heat
Tumor - swelling
Dolor - pain
What causes rubor?
Vascular leakage leads to an accumulation of blood contents, including red blood cells which causes the redness
What causes calor at a site of inflammation?
High metabolism of infiltrating immune cells all generate heat. Also the increased presence of fluid at core body temperature at a site that usually has limited exposure
What is inflammation?
A non specific immune response to cellular injury which is designed to remove damaged cells and clear threats such as infections and pathogens
It is a complex and tightly regulated process
What are the causes of inflammation?
Pathogens, allergens, physical damage, extreme temperatures, auto-antigens, non-apoptotic cell death (necrosis and necroptosis)
What diseases can lead to inflammation?
Infection
autoimmunity
hypersensitivity
trauma
fibrotic disease
cancer
What cells are involved with inflammation?
epithelial and endothelial cells
Neutrophils
macrophages
lymphocytes
eosinophils
mast cells
Where can inflammation occur?
Any vascularised tissue
Is acute inflammation a fast or slow response?
Rapid response, non-specific response to cellular injury
What does acute inflammation lead to?
Change in local blood flow–>
Structural changes in the microvasculature–>
Recruitment/ accumulation of immune cells and proteins
When is inflammation initiated?
When cellular damage leads to the release of Damage Associated Molecular Pathogens (DAMPs) or Pathogen Associated Molecular Pathogens (PAMPs)
What causes swelling at a site of inflammation?
Vascular leakage increases blood flow into the inflamed tissue, leading to tissue buildup
What causes pain in an inflamed area?
Many of the mediators that signal to endothelial and immune cells during inflammation also signal on local nerve cells
What is meant by acute inflammation?
A short term process occuring in response to tissue injury, normally associated with rapid onset and resolution
What is acute inflammation characterised by?
Neutrophil recruitment
What triggers the release of DAMPs and PAMPs?
Non-apoptotic cell death eg due to a wound for example
What vasodilators do mast cells release?
Nitric oxide and histamine
What are the vascular changes associated with the release of histamine and nitric oxide?
- Increase permeability of blood vessel wall
- Dilation
- Plasma leakage
After damage to a steady state of an organ ie., the skin, what 3 things happen?
- inflammatory signals
- non-apoptotic cell death
- detection of foreign material - vasodilators released
- Histamine
- Nitric oxide - vascular changes
- increased permeability
- dilation
- reduced flow
- plasma leakage
What 4 benefits does increased vascular permeability and leakage into an inflamed site bring? BALP
forms a BARRIER
more ANTIBODIES
more LEUKOCYTE migration
more PROTEINS to the site
What are soluble mediators released at injury?
Histamines, prostaglandins, cytokines (TNF, IL-1), Chemokines, Complement (C5a, C3a, C4a)
What are the principle sources and actions of histamines?
mast cells, basophils, platelets
vasodilation, increased vascular permeability, endothelial activation
What are the principle sources and actions of prostaglandins?
mast cells, leukocytes
vasodilation, pain, fever
What are the principle sources and actions of cytokines?
macrophages, endothelial cells, mast cells
endothelial activation (adhesion molecules), fever, malaise, pain, anorexia, shock
What are the principle sources and actions of chemokines?
leukocytes, activated macrophages
chemotaxis, leukocyte activation
What are the principle sources and actions of complement (C5a, C3a, C4a)?
Plasma (produced in the liver)
leukocyte chemotaxis and activation, vasodilation (mast cell stimulation), opsonisation
Why do we experience pain during inflammation?
Due to the release of prostaglandins
How do neutrophils move to areas of damage?
Via chemotaxis, following a concentration gradient of chemotoxins including C5a, LTB4 and bacterial peptides
What is exudate?
Fluid, protein and cells that have seeped out a blood vessel
What does the exudate form?
A separation between healthy tissue and the inflamed tissue - acts as a physical barrier
What is immune cell recruitment?
- recruitment and inflammation signals at the site of damage e.g., chemokines produced
- chemokines diffuse out to form a gradient
- leukocytes expressing complementary chemokine receptors migrate toward the chemokine source
What are examples of immune cell recruitment?
Chemokine: CXCL8 otherwise known as IL-8
Receptors: CXCR1 and CXCR2, g-coupled 7-transmembrane proteins
Cell type: Neutrophils. Often the first cell type recruited to the site of inflammation
How are neutrophils able to migrate towards the chemokine source?
They express complementary chemokine receptors which allow them to migrate towards the course
What is meant by neutrophil extravasation?
The movement of neutrophils from the vasculature into the surrounding tissue to reach the site of inflammation
What are the four steps of neutrophil extravasation?
- Chemo-attraction
- Rolling adhesion
- Tight Adhesion
- Transmigration
What is chemo-attraction?
Cytokines-> endothelial
up-regulation of adhesion molecules
e.g., selectins
What are the two adhesion molecules which are upregulated by cytokines?
P-selectin and E-selectin
How do neutrophils recognise selectin molecules on the endothelium?
They have complementary carbohydrate ligands which bind to the selectin molecules
What is rolling adhesion?
carbohydrate ligands in a low affinity state on neutrophils bind to selectins
e.g., PSGL1 (selectin P ligand) binds P and E-selectins
What is the name of the P selectin ligand?
PSGL1
What is tight adhesion?
Chemokines promote low to high affinity switch to integrins LFA-1, Mac-1- enhance binding to ligands e.g., ICAM-1/2