Chapter 2 - Inflammation, Inflammatory disorders, and Wound healing Flashcards
What characterizes Acute inflammation?
Edema and Neutrophils
What causes acute inflammation?
Infection and tissue necrossis
What are the five main mediators of acute inflammation?
- Toll-like receptors
- Arachidonic acid metabolites
- Mast cells
- Complement
- Hageman factor
What is CD14 recognizing a lipopolysacharide (LPS) an example of?
A TLR (toll-like receptor) recognizing a PAMP (Pathogen-associated molecular pattern).
LPS is found on the outer membrane of gram-negative bacteria.
On what type of immune cells are there TLRs? (Innate vs adaptive)
Both innate and adaptive cells.
What happens when a TLR is activated?
It upregulates NF-kB (“on” button) which activates immune response genes which produces multiple immune mediators.
Which two pathways act upon arachidonic acid after it has been released from the cell membrane, and what releases it?
- Cyclooxygenase pathway which produces prostaglandins.
- 5-lipoxygenase pathway which produces leukotrines.
- Phospholipase A2
Which prostaglandin mediates fever and pain?
PGE2 mediates fEver and pain
Which physiological responses are mediated by both PGI2, PGD2, and PGE2?
Vasodilation of the arterioles and increase of vascular permeability in the post capillary venules.
Which mediators attracts and activates neutrophils?
LTB4, C5a, IL-8, and bacterial products.
What is mediated through the leukotrines LTC4, LTD4, and LTE4?
They cause smooth muscle contraction: vasoconstriction of the arterioles, bronchospasm, and increased vascular permeability through the pericytes.
What are the 3 methods of mast cell activation?
- Tissue trauma
- Complement proteins; C3a and C5a
- Cross linking cell-surface IgE by antigen
Which mediator is released from the mast cells and what does it cause?
Histamin, causes vasodilation of arterioles and increased vascular permeability.
Which three individual pathways are able activate the complement cascade, and how do they work?
- Classical pathway: C1 binds to IgG or IgM (general motors makes classic cars) that is already bound to an antigen, creating C3 convertase.
- Alternative pathway: Microbial products directly bind complement, creating C3 convertase.
- Lectin pathway: Mannose-binding lectin (MLB) binds to mannose on icroorganisms and activate complement, creating C3 convertase.
What is the sequence of the activated complement cascade, and what do the mediators produce?
C3 convertase mediates C3 → C3a and C3b. C3b produce C5 convertase which mediates C5 → C5a and C5b.
- C5b complexes with membrane attack complex (MAC) and lyse the microbes
- C3a and C5a trigger mast cells.
- C5a is chemotactic for neutrophils, together with LTB4, IL-8, and bacterial products.
- C3b is an opsonin for phagocytes
Hageman factor takes part in the activation of three major systems, which?
- Coagulation and fibrinolytic system (factor XII)
- Complement system
- Kinin system: plays a role in creating bradykinin which mediates vasodilation, increased vascular permeability and pain.
What are the 5 signs of inflammation and what mediates them?
- Rubor and Calor: are both caused by increased blood flow through smooth muscle relaxation. Key mediators are histamine, prostaglandines, and bradykinin.
- Tumor: caused by leakage of fluid from the post capillary venules (histamin, PG, LT, or tissue trauma)
- Dolor: Sensitization of nerve endings by bradykinin and PGE2.
- Fever: is mediated through Pyrogens mediated increase in cyclooxygenase activity in the thalamus or through PGE2 mediation.
What are the seven steps of Neutrophil arrival and function?
1. Margination
2. Rolling
3. Adhesion
4. Transmigration and chemotaxis
5. Phagocytosis
6. Destruction of phagocytosed material
7. Resolution
Which mediators take part in Margination?
Margination occurs through the change in flow during vasodilation. Mediators of vasodilation are bradykinin,histamin, and theprostaglandins.
Which mediators take part in Rolling?
Rolling is the decrease in speed, achived by the selectin“speed bumps”. P-selectin is released from Weibel-Paladebodies (VonWillebrandt factor) which is mediated by Histamins. E-selectin is induced by TNF and IL-1.
Which mediators take part in Adhesion?
Interaction between CAMs and Integrins are what causes adhesion. CAMs are upregulated by TNF and IL-1, while integrins are upregulated by C5b and LTB4.
Case: An 18 month old patient presents with it’s third E. coli mediated UTI in four months.
The family history does not indicate a significant risk of UTIs.
Tests show a high circulating neutrophil count.
In the patient notes it is documented that the umbillical cord was slow to detach.
Leukocyte adhesion deficiency is an autosomal recessive defect of integrins. It effects the bodies ability to adhere neutrophils to the blood vessel walls. This causes a dysfunction of the acute inflammation state (destroys the dead tissue in the umbillical cord), and depleation of the marginated pool (does not attach), as well as an inability to form pus (dead neutrophils+fluids).
Which mediators aid in migration and chemotaxis?
Bradykinin, histamin, leukotrines, and prostaglandins causes increased permeability of the blood vessel walls. Bacterial products, IL-8, C5b, and LTB4 are chemotaxins, they attract neutrophils.
Which mediators facillitate phagocytosis?
IgG and C3b work as opsonins, tagging organisms for phagocytosis.
Case: Patient presents with impetigo. On blood test you find a low neutrphil count and giant granules in the leukocytes on histology. The patient also suffers from albinism. What is the underlying condition?
Chediak-Higashi syndrome, protein tracking deffect leading to impairment of phagolysosome formation.