Week 1: Inflammation and repair 1 Flashcards
Define inflammation
A localised response resulting color,tumor, rubor, dolor and function laesa due to infection or injury.
What is the purpose of inflammation?
Protective response against damage/pathogens
Trigger homeostasis
What is the mechanism behind calor, rubor and tumour in inflammation?
Vasodilation increases blood flow
Increased vascular permeability and causes vascular status
More blood closer to the surface
Friction from diapedisis may also contribute to heat
What is the mechanism behind dolor from inflammation?
Action of inflammatory mediators on free nerve endings to activate or sensitize the endings.
Typically prostaglandins (leukocyte release) and bradykinin released from mast cells.
What causes functio de laesa during inflammation?
Damage to cells necessary for tissue function including parenchymal and stromal cells
What are the kinetics of acute inflammation?
Rapid and short lived reponse to injury.
Develops over minutes/hours
May persist over a few days
Starting with edema, neutrophil infiltrate the monocyte/macrophage infiltrate
What is the process behind vasodilation in inflammation?
Microbes/ nectrotic tissue release PAMPs/DAMPs that are recongised by PRR on tissue resident immune cells.
Results in the release of inflammatory mediators
In particular histmane release from mast cells.
Histamine binds to H1 receptors on endothelial cells, results in the production of NOx. NOx results in the relaxation of smooth muscle in capillary walls - acting as a vasodilator
What are the key phsyiological features of acute inflammation?
Vasodilation
Increased vascular permeability
Vascular statis
Pain
What is the mechanism behind increased vascular permeability during inflammation?
Vasodilation
Inflammatory mediators such as histamine, prostaglandins and leukotrienes cause endothelial cells to contract, disrupting the tight junctions to widen the gaps.
What is the mechanism behind vascular statis in acute inflammation?
Increased vascular permeability - loss of fluid from blood plasma
This increases the viscosity of blood hence slower flow
Fibrin clots may also form - due to increased pro-coagulant factors such as fibrinogen and thromboxane
What is the process of leukocyte extraversion in inflammation?
Vasodilation and increased vascular permeability from inflammatory mediators.
Vascular stasis allows immune cells to lone up near endothelium (imagination)
Leukocyte forms low affinity bonds with the endothelial walls by E-selectin on endothelial cells and sialyl-Lewis on leukocyte, alongside L selecting on leukocyte walls and ligand on endothelial cells.
Breaking and reformation of these bonds allows the leukocyte to roll along endothelium.
Chemokine signalling in leukocyte cause a higher affinity adhesion molecule, this tighter bond is where the leukocyte will pass through widened gaps in the endothelial layer (from endothelial cell contraction), squeezing into intersitial fluid by diapedesis (may secrete collagenases to help degrade BM)
Follows chemokine gradient to site of injury, chemokines rearrange the cytoskeleton of the lymphocyte to allow it to move forward.
Basophil
What is the process by which a macrophage can lead to pain sensation?
A resident activated macrophage releases inflammatory mediators such as TNF and PGE2, which bind to cytokine receptors on the surface of nociceptor terminals.
Leads to a cascade of signalling inside the nocicpetor including the activation of adenylate cyclase.
This leads to increased Ca2+ mobilisation
Increased voltage or ligand gated channel activation
Increased neuropeptide transcription and release
Increased transcription or receptor and channel proteins.
Leads to sensitisation to or activation of a pain signal
Lymphocyte
Monocyte
Macrophage
Eosinophil
What are the main cell types involved in acute inflammation?
Neutrophils
May be followed by monocytes and macrophages (typically in smaller numbers)
What is the role of neutrophils in acute inflammation?
Dominate for 6-24 hours
Die and replaced by monocytes
Phagocytose pathogens, debris and dead cells, will secrete cytokines and produce NETs