Topics A22-25 - Inflammation (Acute, Chronic, Granulomatous) Flashcards
Classical symptoms of acute inflammation
Rubor, tumor, calor, dolor, loss of function
All occur due to increased blood content of inflamed tissue (historically this was the reason behind bloodletting)
Why does pain occur during inflammation?
Which part of the immune system is inflammation, innate or adaptive?
PGE2 sensitizes nerve endings to effects of bradykinin and other pain receptors
Immune system is part of Innate immunity
What are 4 major stimuli for inflammation?
- Infections
- Immune reaction, as in to a bee sting
- Tissue damage/ necrosis: from trauma, radiation, burns
- Foreign bodies: sutures, splinters, etc
What are the 3 major steps of acute inflammation (according to the lecture)
- Hyperemia: arteriole arteriole dilation + reduced venous outflow + capillary dilation. Flow of blood slows down at inflammation site, allowing for more interaction
- Exudation: Components of blood leak out into EC matrix due to increased capillary permeability (exudate = high protein)
- Cell migration: chemotaxis etc of protective and regenerative cells
What regulates the early phase of exudation in inflammation? What regulates the late phase?
Early: histamine, bradykinin, leukotrienes
Late: TNF, IL-1, IFN gamma
How does an inflammasome get activated? What is the effect?
Inflammasomes detect products of dead cells from pathogenic bacteria via extracellular ATP and uric acid.
Inflammasome includes caspase-1, which activates IL-1 beta. IL-1B is a major pro-inflammatory cytokine
What are the 4 steps of leukocyte recruitment?
- Margination / Rolling along vessel wall
- Adhesion to endothelium
- Migration between endothelial cells / Diapedesis
- Migration to interstitial tissues towards a chemotactic stimulus
What type of molecules mediate rolling?
What type of molecules mediate adhesion?
Rolling = selectins on leukocytes and endothelial cells
Adhesion = leukocyte integrins + endothelial cells CAMs (cellular adhesion molecules: VCAM-1, ICAM-1 etc)
Where in the vasculature does diapedesis normally occur?
In the systemic venules (high endothelial venules - HEV)
Also occurs in pulmonary capillaries
What are 4 things (either exogenous or endogenous) that can induce chemotaxis?
- Bacterial products, especially peptides with N-formyl methionine termini
- Cytokines, especially chemokines like IL-8
- Complement components: C5a especially
- Products of lipoxygenase pathway, especially leukotriene B4
Which type of leukocytes dominate in the first 6-24 hours of inflammation?
Which ones replace them afterwards?
What are some exceptions?
Neutrophils first, monocytes later, and lymphocytes usually even later on
However, in viral infections, lymphocytes may arrive first; and in hypersensitive reactions it may be eosinophils. Also, Pseudomonas infections have continuous neutrophils
What is the mechanism behind the two types of leukocyte adhesion deficiency (LAD?)
LAD-1: defective synthesis of beta 2 integrin (binds to ICAMs)
LAD-2: deficiency of endothelial cell selectin that normally binds neutrophils. Milder symptoms than type 1.
What is the first sign of leukocyte adhesion deficiency (LAD)?
Delayed separation from umbilical cord: neutrophils are important for cord separation.
They originally noted that babies who couldn’t get rid of their umbilical cord would get sick and die of infection at a very young age
What are 3 major ways that the immune system recognizes infection, but also necrotic cells and foreign substances? (one was already asked about).
- Toll-like receptors (TLR) - has receptors both on the membrane and internally. Various TLRs detect endotoxins, bacterial DNA, viruses, etc.
- Lectin receptors: MBL on complement etc
- Inflammasome: detects products of dead cells, like uric acid and extracellular ATP
How do neutrophils and macrophages actually cause harm with inflammation?
These leukocytes secrete degradative enzymes and ROS, killing microbes but also damaging normal cells - “innocent bystanders”
Attempts to reperfuse necrotic areas may cause more damage via this mechanism, including hemorrhage. This is also involved in carcinogenesis.
What is the source and effect of histamine in acute inflammation?
Source: mast cells, basophils, platelets
Effect: vasodilation, increased vascular permeability, endothelial activation
What is the source and effect of serotonin in acute inflammation?
Source: platelet granules, released during platelet aggregation
Effect: vasoconstriction
What is the source and effect of prostaglandins in acute inflammation?
Source: mast cells, leukocytes
Effect: vasodilation, pain, fever (esp PGE2)
What is the source and effect of leukotrienes in acute inflammation?
Source: mast cells, some leukocytes
Effect: increased vascular permeability, vasoconstriction, chemotaxis, leukocyte adhesion and activation.
Which leukotrienes cause vasoconstriction and increased vascular permeability?
Which cause chemotaxis and leukocyte adhesion?
Vasoconstriction and increased vascular permeability: Leukotriene C4, D4, E4
Chemotaxis and leukocyte adhesion: Leukotriene B4 (very potent neutrophil attractor, and also secreted by neutrophils and some macrophages)
What are 3 important categories of proteins / protein fragments that are produced by the liver and play a role in acute inflammation?
- Complement proteins: cause leukocyte activation and chemotaxis, directly kill microbes (MAC), and stimulate mast cells to cause vasodilation
- Kinins: cause pain, vasodilation, increased vascular permeability
- Coagulation factors: also play a role in activating endothelial cells and recruiting leukocytes
What are the major cytokines in acute inflammation?
TNF, IL-1, IL-6, and chemokines
What are the sources and some more local roles of TNF and IL-1 in acute inflammation?
Sources: activated macrophages, mast cells, endothelial cells, and some others. Inflammasomes make IL-1.
Roles: endothelial activation, increased leukocyte binding and recruitment, enhanced production of additional cytokines. TNF increases thrombogenicity, IL-1 activates tissue fibroblasts and stimulates production of IL-6