CH2 - Inflammation, Inflammatory Disorders, and Wound Healing Flashcards
What does inflammation allow?
Allows inflammatory cells, plasma proteins (e.g., complement), and fluid to exit blood vessels and enter the interstitial space
Inflammation is divided into what?
Divided into acute and chronic inflammation
What is inflammation characterized by?
the presence of edema and neutrophils in tissue
Inflammation arises in response to what?
infection (to eliminate pathogen) or tissue necrosis (to clear necrotic debris)
innate immunity
Immediate response with limited specificity
What are the mediators of acute inflammation?
Toll-like receptors, Arachidonic acid (AA) metabolites, Mast cells, Complement, Hageman Factor
Toll-like receptors
Present on cells of the innate immune system (e.g., macrophages and dendritic cells)
How are TLRs attivated?
pathogen-associated molecular patterns (PAMPs) that are commonly shared by microbes, CD14 (a TLR) on macrophages recognizes lipopolysaccharide (a PAMP) on the outer membrane of gram-negative bacteria
TLR activation results in what?
upregulation of NF-kB, a nuclear transcription factor
What does NF-kB do?
activates immune response genes leading to production of multiple immune mediators
TLRs and chronic inflammation?
They are also present on cells of adaptive immunity (e.g., lymphocytes) and play an important role in mediating chronic inflammation.
Arachidonic acid (AA) metabolites
- AA is released from the phospholipid cell membrane by phospholipase A2 and then acted upon by cyclooxygenase or 5-lipoxygenase.
Cyclooxygenase
produces prostaglandins (PG) a. PGI2, PGD2 and PGE2 mediate vasodilation and increased vascular permeability. PGE2 also mediates pain.
5-lipoxygenase
produces leukotrienes (LT) a. LTB4 attracts and activates neutrophils. b. LTC4, LTD4 and LTE4 (slow reacting substances of anaphylaxis) mediate vasoconstriction, broncho spasm, and increased vascular permeability.
Where are Mast cells located?
- Widely distributed throughout connective tissue
How are Mast cells activated?
(1) tissue trauma (2) complement proteins C3a and C5a (3) cross-linking of cell-surface IgE by antigen
Mast cells immediate response is?
involves the release of preformed histamine granules, which mediate vasodilation of arterioles and increased vascular permeability
Mast cells delayed response is?
involves production of arachidonic acid metabolites, particularly leukotrienes.
Complement
proinflammatory serum proteins that complement inflammation
Where is complement located?
Circulate as inactive precursors;
Activation of complement occurs via what?
Classical pathway, Alternative pathway, MBL pathway
Classical pathway
C1 binds IgG or IgM that is bound to antigen
Alternative pathway
Microbial products directly activate complement.
Mannose binding lectin pathway
mannose binding lectin (MBL) pathway MBL binds to mannose on microorganisms and activates complement
All pathways of complement result in?
production of C3 convertase (mediates C3?>C3a and C3b, producing C5 convertase (mediates C5?>C5a and C5b)
What forms the MAC?
C5b complexes with C6-C9 to form the membrane attack complex (MAC)
C5a
chemotactic for neutrophils
C5b
opsonin for phagocytosis
MAC
Lyses microbes by creating a hole in the cell membrane
Where is Hageman factor (Factor XII) produced?
Inactive proinflammatory protein produced in liver
How is Hageman factor (Factor XII)?
Activated upon exposure to subendothelial or tissue collagen;
Hageman factor (Factor XII) activates what?
- Coagulation and fibrinolytic systems 2. Complement 3. Kinin system
Kinin system
Kinin cleaves high-molecular-weight kininogen (HMWK) to bradykinin, which mediates vasodilation and increased vascular permeability (simitar to histamine), as well as pain.
What are the cardinal signs of inflammation?
Redness (rubor) and warmth (calor), swelling, pain, fever
What is Redness (rubor) and warmth (calor) due to?
- Due to vasodilation, which results in increased blood flow
How does Redness (rubor) and warmth (calor) occur?
Occurs via relaxation of arteriolar smooth muscle;
Key mediators of Redness (rubor) and warmth (calor) are?
histamine, prostaglandins, and bradykinin
Swelling (tumor) is due to what?
Due to the leakage of fluid from postcapillary venules into the interstitial space (exudate)
What are the Key mediators of swelling?
(1) histamine, which causes endothelial cell contraction and (2) tissue damage, resulting in endothelial cell disruption,
Pain (dolor)
Bradvkinin and PGE2 sensitize sensory nerve endings.
Fever
- Pyrogens (e.g., LPS from bacteria) cause macrophages to release IL-1 and TNF, which increase cyclooxygenase activity in perivascular cells of the hypothalamus, 2. Increased PGE2 raises temperature set point.
What are the steps in neutrophil arrival?
Margination, Rolling, Adhesion, Transmigration and Chemotaxis, Phagocytosis, Destruction of phagocytosed material, resolution
Step 1?Marginatum
- Vasodilation slows blood flow in postcapillary venules. 2. Cells marginate from center of flow to the periphery.
Step 2?Rolling
- Selectin speed bumps are upregulaled on endothelial cells. 2. Selectins bind sialyl Lewis X on leukocytes. 3. Interaction results in rolling of leukocytes along vessel wall
P-selectin is released from where and what does it mediate?
release from Weibel Palade bodies, is mediated by histamine.
E-selectin is induced by what?
TNF and IL-1.
Step 3?Adhesion
- Cellular adhesion molecules (ICAM and VCAM) are upregulated on endothelium by TNF and IL-1 2. Integrins are upregulated on leukocytes by C5a and LTB4 3. Interaction between CAMs and integrins results in firm adhesion of leukocytes to the vessel wall
Step 4?Transmigration and Chemotaxis
- Leukocytes transmigrate across the endothelium of postcapillary venules and move toward chemical attractants (chemotaxis).
Neutrophils are attracted by
bacterial products, IL-8, C5a, and LTB4
Step 5?Phagocytosis
- Consumption of pathogens or necrotic tissue; phagocytosis is enhanced by opsonins (IgG and C3a). 2. Pseudopods extend from leukocytes to form phagosomes, which are internalized and merge with lysosomes to produce phagolysosomes.
Step 6?Destruction of phagocytosed material
- O2-dependent killing is the most effective mechanism. 2. HOCl generated by oxidative burst in phagolysosomes destroys phagocytosed microbes.
Step 7?Resolution
Neutrophils undergo apoptosis and disappear within 24 hours after resolution of the inflammatory stimulus.
Macrophages
Macrophages predominate after neutrophils and peak 2-3 days after inflammation begins.
What are macrophages derived from?
monocytes in blood