Flashcards in Inflammation 4/24 Deck (135):
four signs of acute inflammation
* noted by Aulus Cornelius Celsus
functio laesa (loss of fn)
- Galen of Pergamon
definition of inflmmation
inflammation having rapid onset and coming to a crisis relatively quickly, with a clear and distinct termination
- may also be defined by inflammatory cells involved (granulocytes)
1. Vascular dilatation and increased flow
2. Microvasculature alterations to allow egress of cells and proteins
3. Emigration, accumulation and activation of leukocytes
Lewis triple response
1. Red line (vasodilation)
2. Red flare (after 15-30 seconds) - vasodilation
3. Wheal in 1-3 minutes (vascular leakage)
- discovered inflammation can be stopped by cutting the nn. surrounding the area
what triggers acute inflammation?
- infections: toll-like and cytoplasmic receptors
- necrotic tissues
- hypoxia (via HIF-1alpha)
- foreign bodies
- immune reactions
need to be able to distinguish granulocyte types ...
- pseudomonas: longer period of neutrophil dominance
- viruses: see lymphocytes
- hypersensitivities: see eosinophils
acute vs. chronic inflammation, what are the cells seen?
acute: eos and neutrophils
chronic: no segmented nuclei, lymphocytes or macrophages
** know slide 10 and 11, how to recognize cell types **
what are series of events in process of inflammation?
1. vasodilation: leads to greater blood flow to area of inflammation, resulting in redness and heat
2. vascular permeability: endothelial cells become "leaky" from direct endothelial injury or via chemical mediators (histamine, bradykinin, leukotrienes)
3. exudation: fluid, proteins, RBCs, and WBCs escape from the intravascular space as a result of increased osmotic pressure extravascularly and increased hydrostatic pressure intravascularly
4. vascular stasis: slowing of the blood in the bloodstream with vasodilation and fluid exudation to allow chemical mediators and inflammatory cells to collect and respond to the stimulus
what alters with vascular flow and vessel caliber in acute inflammation?
1. vasodilation following transient constriction
2. increased permeabiliy resulting in fluid loss
3. fluid loss and increased vessel diameter results in slower blood flow (stasis)
4. leukocytes accumulate along endothelium
What is the stimuli for acute inflammation?
1. infections: TLR
2. Necrotic tissues: release chemicals like uric acid, ATP, HMGB-1 and DNA
3. hypoxia: results in release of HIF1-alpha (this induces production of VEGF and increases vascular permeability)
4. foreign bodies
5. immune rxns
what are the four steps in process of inflammation?
1. vasodilation: greater bloodflow and inflammation (caused by histamine and NO): produces redness and heat
2. vascular permeability: endothelial cells become leaky either due to direct injury or to chemicals such as histamine, bradykinin and leukotrienes
3. exudiation: fluid, proteins, RBCs and WBCs
4. vascular stasis: with increased vessel diameter and viscosity of blood
redness and heat of inflammation
- produced by NO and histamine
what are four principle mechanisms for increased vascular permeability?
1. contraction of endothelial cells (short-lived, induced by histamine and NO and substance P) = "immediate transient response"
2. endothelial injury (may be long lived)
3. leukocyte-mediated vascular injury (late stages of inflammation)
4. increased transcytosis (vascular permeability induced by VEGF)
what does VEGF do?
increased vascular permeability - allows for neutrophils to enter the inflamed tissues
first responders of acute inflamation
- see segmented lobes 3-5 present
- seen with viral infections
- interact w/ Ag presenting cells and are part of direct aquired immune response
- release lymphokines
- visualized as one large richly stained purple nucleus (very little plasma)
seen in chronic inflammation
- visualized as one "u-shaped" or kidney shaped nucleus
- seen with hypersensitivity reactions
- produced in bone marrow and regulated by ILK 3 and 5
- granule consists of Major Basic Protein (toxic to parasitic helminiths)
see 1-3 lobes, they are reddish and granular, and the lobes are not connected
- just see granulations, no nucleus visualized
- stores and releases histamine and heparin
what is reaction of blood in response to inflammation?
1. vasodilation: increased warmth/heat
2. increased vascular permeability: extravasation and of fluids and proteins
3. fluid loss and increased vessel diameter --> stasis
4. leukocyte emigration and accumulation at site of injury
what causes increased vascular permeability?
VEGF and NO
ultrafiltrate plasma leaking from vessels due to increased hydrostatic pressure or oncotic pressure
- thin and watery/ w/out tissue fragments
- clear and without large amount of proteins
- low cell count
- no bacteria or inflammation
- mixture of cells and plasma leaking out of vessels in response to chemical mediators
- large amount of protiens
- bacteria and inflammation may be present
= pussy exudate, contains large amount of neutrophils
clear with some reddish tinge
full of blood
greenish/ many neutrophils
intermediate transient response
this occurs when scratched (i.e. redmarks)
- leakage starts, due to small venules endothelial cells contracting
- venules contract due to histamine, bradykinin, serotonin, leukotrienes and substance P
- leakage lasts 15-30 mins
immediate sustained response
- leakage starts with injury and may last hours to days
- endothelial cell necrosis occurs
- leakage continues for a long time
delayed prolonged leakage
- inflamm. can last hours to days and leakage starts 2-12 hours after injury
- capillaries and venules are affected
inflamation of lymph vessels
inflammation of vessels and lymph nodes
inflamm. of lymph nodes
steps of recruitment of leukocytes?
1. margination, rolling, adhesion to endothelium
2. migration across endothelium and vessel wall
3. migration in the tisues toward chemotactic stimulus
steps involved in leukocyte migration:
1. macrophages with microbes secrete IL-1 and TNF which act on endothelial cells.
2. endothelial cells express E-selectin and P-selectin which weakly interact with leukocytes and cause rolling
3. endothelial cells express (ICAM-1 and VCAM-1) which bind integrins of leukocyte initiating activation and adherence
4. diapedesis occurs due to CD31 and CD99 - adhesion molecules
what binds what during lymphocyte rolling?
TNF and IL-1 start the process
1. E-selectin and P-selectin (EC) binds sialyl-Lewis X (L)
2. L-selectin (L) binds Glycam-1 (EC)
what binds during adnesion/activation?
- mediated by IL-1 and TNF
ICAM-1 (EC) binds CD11/18 integrin (L)
VAM-1 (EC) binds VLA-4 integrin (L)
what adhesion molecules needed for diapedesis?
CD31 (PECAM): adhesion molec
CD99: normally repulses cells, but changes to hemophillic state and is adhesive
storage of granules of endothelial cells which store P-selectin
- the P-selectin is redistributed on the endothelial cell surface in response to histamine and thrombin
located in extracellular matrix, allows leukocytes to be retained in the area that they are needed
what are endogenous and exogenous agents causing chemotaxis?
exogenous = bacterial products
- cytokines (IL-8)
- Leukotriene B4 (LTB4)
* all of these agents bind specific GPCR on leukocytes, resulting in increased cystolic CA++ and kinases and polymerization of actin and filopodia for leukocyte migration
bacterial formyl-peptides attract what cells?
PMNs and macrophages
C5a chemotactant to what
PMNs and macrophages
LTB4 chemotactant to what?
viral infections see what first?
pseudomonas bacterial infection see what?
neutrophils for 2-4 days
what are normal responders to inflammation?
Nphils: 6-24 hours
Mphages: 24-48 hours
what do leukocytes express for recognition of microbes and dead tissues?
1. TLRs: recognize LPS and other microbes
2. GPCRs: recognize bacterial peptides containing N-formylmethionyl residues
3. receptors for opsonins (antibodies and C' proteins)
4. receptors for cytokines: most important is interferon gamma which is secreted by NK cells reacting with microbes
note: CD14 binds LPS of microbes and is also a recognition target
what does interferon gamma do?
- secreted by NK cells that interact with microbes
- activates macrophages to kill
- major macrophage activating cytokine
steps seen in phagocytosis?
1. recognition of target and attachment: mannose receptors, scavenger receptors, GPCR, TLRs, LPs binding of CD14
2. engulfment: pseudopods engulf around particle and PM is cut off to create a phagosome vesicle. phagocytosis reqs polymerization of actin filaments.
3. killing and degredation:
phagosome fuses with lysosome --> phagolysosome. killing occurs through respiratory burst of ROS
Note: H2O2-MPO-halide system is most efficient bactericidal system of neutrophils, where H2O2 is converted to OH
Leukocyte adhesion deficiencies
defective leukocyte adhesion b/c of mutations with integrins and selectins
- autosomal recessive condition due to defective fusion of phagosomes and lysosomes (causing increased infections)
- abnormal melanocytes (albinism)
- decreased neutrophils (netropenia) and defective degranulation
- leukocytes contain giant granules due to aberrant phagolysosome fusion
- defect in LYST gene
decreased microbial killing b/c of defective MPO-H202 system
chronic granulomatous disease
decreased oxidative burs due to problems with microbicidal activity
- see decreased NADPH oxidase, causing decreased ROS, causing decreased MPO and resulting in increased candida infections
what are measures to end inflammation/
passive: neutrophils have short lifespan and there is decrease in cytokines released
- switch in AA production
- liberation of anti-inflamm cytokines (TGF beta)
- anti-inflamm. lipid mediators (resolvins and protectins)
- decreased TNF production by macrophages (due to neural changes)
- preformed vasoactive amine stored in mast cells (and basophils and platelets)
- dilates arterioles and increases endothelial contraction and vascular permeability
- constriction of large aa.
- released in response to physical injury, neuropeptides, Av vinding, C'proteins, cytokines (IL-1 and IL-8)
what causes release of histamine?
1. physical injury - triple response
2. neuropeptides - substance P
3. Ab binding
4. anaphylatoxins (C3a and C5a)
5. cytokines (IL1 and IL8)
- released by platelets in neuroendocrine enterochromaffin cells - NOT MAST CELLS
- causes vasodilation and increased vascular permeability
** link between clotting and inflammation **
stimuli for release of seratonin?
release comes from aggregated platelets.
- Antigen binding complexes
produced from AA --> COX1/COX2 --> prostaglandin --> TXA2
- causes vasoconstriction and promotes platelet aggregation
- produced by platelets
what do steroids inhibit?
phospholipases; these are needed to create AA
- thus they can reduce inflammatory effects
what are produced by cyclooxygenases?
- TXA2 (platelet aggregation and vasoconstriction)
- PGI2 (inhibits platelet aggregation, vasoconstriction)
- PGE2 (pain)
- made by endothelium from Cyclooxygenase
- inhibits platelet aggregation and causes vasodilation
prostaglandin that attracts neutrophils, vasodilates and causes pain and fever
the main prostglandin causing pain!
- also vasodilates
made from AA (requires 5-lipoxygenase)
- chemotaxis, aggregation and adhesion
- attracts leukocytes
cause vasoconstrcition, bronchospasm, increased vascular permeability
Lipoxins (LXA4, LXB4)
- precursors are produced by leukocytes and converted by platelets
- inhibit neutrophil adhesion and chemotaxis
- inhibit inflammation (may play a role in resolution of inflammation)
what is main mediator for vasodilation?
PGI2, PGE2 (prostacyclin and prostaglandins)
major mediator for vasoconstriction?
thromboxane A2 (TXA2)
major mediator for chemotaxis
leukotriene B4 (LTB4)
COX1 (and COX2) inhibitor: prevents clotting through inhibiting formation of thromboxane.
- also impairs vasoconstriction (increased vasodilation)
- prevents clotting (decreased clotting)
COX2 inhibitor: impairs endothelial cel production of prostacyclin
- prevents vasodilation and promotes platelet aggregation (clotting)
- used to treat arthritis b/c it acts as an anti-inflammatory agent
- can cause thrombosis as side effect
inhibits production of lipoxins (which inhibit neutrophil adhesion and chemotaxis)
- used to treat asthma
platelet activating factor
made by platelets, endothelial cells and leukocytes
*** results in platelet aggregation ***
- vasoconstiction and bronchoconstriction in large amounts
- vasodilation and increased vascular permeability at low amounts
- enhanced luekocyte adherence to endothelium
COX1 vs COX2
COX1 is constitutively expressed in most tissues and is produced in response to inflamm. stimulus (results in production of thromboxane --> platlet aggregation and vasoconstriction)
COX2 is absent in most tissues at rest, has anti-inflammatory effect (prostacyclin)
broad spectrum inhibitors that block the conversion of arichidonic acid via phospholipases
how does ROS affect smokers?
ROS accumulate and inactivate alpha1-antitrypsin which normally protects against neutrophil elastase
- results in decrease in lung elasticity and development of emphysema
- secreted by endothelium and macrophages
- relaxes smooth muscle
- inhibits leukocyte rolling, adhesion and degranulation
- inhibits platlet aggregation and adhesion
- inhibits mast cell activation and release of histamine
eNOS (endothelium), nNOS (neurons), iNOS (macrophages)
- secreted by ***macrophages***, mast cells, t lymphocytes
- stimulates expression of endothelial adhesion molecs and secretion of other cytokines
- stimulates acute phase response, fever, activates fibroblasts and neutrophils
- regulates energy balance
- when sick, you have decreased appetite
- this is due to increased TNF amounts, which regulates energy balance
comes from macrophages
- similar to TNF, plays a greater roll in fever
- stimulates expression of adhesion molecs and stimulates acute phase response
- "inflammasomes" control its production through stimuli of microbes and dead cells (activates caspase proteases that cleave IL-1)
inherited autoinflammatory syndromes - i.e. mediterranean fever
- mutant proteins activate caspases of inflammasomes, resulting in unregulated cleavage of IL-1
- patients present with fever, inflammation without provocation
- used to treat with IL-1 antagonist
chemokines resp. for acute phase reaction?
IL-1 and TNF
- secreted by macrphages
- increased leukocyte adherence
- activation of leukocytes
- increased collagen synth
- increased fever, decreased appetite, increased sleep
- increased acute phase proteins: CRP and hepcidin
causes anemia during acute phase reaction b/c it binds iron and patient appears iron deficient
def of cytokines
general category of messengers - operates in paracrine manner
def of chemokines
special cytokines that direct leukocyte adhesion
what is contained in cytoplasmic granules of neutrophils and monocytes?
primary granules: Azurophil granules - contain bactericidal lysozymes, defensis
specific granules: secondary: contain enzymes responsible for digestion
- involved in mast cell activation
- neurons containing this are present in lungs and GI
- mast cell activation and histamine release
- vascular permeability
what does Hageman factor do?
sets off four responses:
1. kinin cascade (bradykinin production)
2. clotting cascade
3. fibrinolytic system
4. complement cascade
Complement cascade: 3 most important mediators?
C5b-B9: membrane attack complex (MAC) - lyses bacteria and cells
C5a and C3a: anaphylatoxins that cause histamine release and increase vascular permeability
C5a also causes leukocyte activation and vasodilation
C3b: opsonin (enhances phagocytosis)- deposited on surface of microbe
three ways to activate complement cascade?
1. microbe binds C3 (alternative)
2. antibody binds microbe (classical)
3. mannose-binding lectin binds microbe (lectin pathway)
- all three result in C3b being deposited on microbe and release of C3a and C5a which recruit leukocytes to kill.
- C3b can be directly phagocytosed by phagocyte
- C3b can also result in formation of MAC omplex and result in lysis of microbe
what causes C3a and C3b to float around?
- plasmin from fibrolytic system.
- this is induced by hageman factor
- Factor XII is activated upon interaction with collagen, BM, or activated platelets
- induces the clotting cascade which will eventually cause prothrombin to be changed to thrombin (via factor X)
- thrombin converts fibrinogen to fibrin which allows for clotting to occur
- results in acute inflammation
Factor XII is activated upon reacting with collagen and exposed BM and converts prekalikrein to kallikrein
- kallikrein will produce bradykinin (PAIN)
- kallikrein feeds back to activate Factor XII further
increases vascular permeability
- causes smooth muscle contraction
- Factor XII is activated by exposed collagen and BM and results in clotting cascade and eventual production of Fibrin.
- Kallikrein also promotes the formation of plasminogen to plasmin
- plasmin breaks down fibrin and forms fibrin split products, thereby increasing vascular permeability and chemotactics
- plasmin also splits C3 (C3b is an opsonin, C3a is an anaphylatoxin)
- plasmin activates hageman factor (increased cogulation and increased inflammation)
cause increased vascular permeability
- histamine and seratonin
- C3a and C5a (liberate histamine from mast cells)
- substance P
cause chemotaxis, leukocyte recruitment and activation
- TNF, IL-1
- C3a, C5a
prostaglandins (mostly PGE2)
cause tissue damage
lysosomal enzymes of leukocytes
morphologic hallmarks of acute inflammation?
- dilation of small blood vessels
- slowing of blood flow
- accumulation of neutrophils
- - fluid extravasation
- limited tissue injury
- acute inflamm. often seen after burn or viral injury
- marked by copious amounts of effusion of non-viscous serous fluid, often seen with blisters
- fluid is yellow
- subtype is urticarial hives
Purulent (supporative) inflammation
acute inflammation that contains exudate
- results in large amount of pus, consists of neutrophils, dead cells and liquefactive necrosis
- will see vascular congestion of blood vessels and stasis
- can result in abscess formation: localized collection of purulent inflamed tissue with central area of necrosis and walled off by fibroblasts and neutrophils
- acute inflammation that results in large increased vascular permeability allowing fibrin to pass through the blood vessels
- fibrin appears as an eosinophilc meshwork
- seen in fibrinous pericarditis (surface looks shaggy, will appear very pink under microscope)
- seen in endocarditis
- if fibrin is not removed, may stimulate ingrowth of fibroblasts and scarring
- acute inflammation near epithelium resulting from necrotic loss of tissue from surface, exposing lower layers
- produced by sloughing of necrotic tissue
- seen in subcu, tissue of lower extremities, mouth, stomach and GI
(Pseudo) Membranous inflammation
- acute inflammation, that is a form of exudative inflammation involving serous and mucous membranes
- fibrin in the exudate causes membrane-like covering that is adherent to inflamed tissue
- seen with C. difficile and C. diptheriae candida infections.
- occurs to people who kill off gut flora who are constantly on antibiotics
what do you see with chronic inflammation?
- macrophages, lymphcytes and plasma cells (mononuclear cells)
- tissue destruction
- CT replacement, fibrosis, angiogenesis
causes of chronic inflamm?
prolonged toxic exposure
see high amounts of lymphocytes, not neutrophils even though this is acute
- can live in tissues for months to years
- appear within 48 hours of infection
- activation resluts in increased ROS and increased tissue damage and inflammation
another name for macrophages:
- alveolar macrophages
- microglia: CNS
- kuppfer cells: liver
- osteoclasts: bone
- dendritic cells (including langerhans cells of skin): Ag presenting cells in tissues
classic activation of tissue macrophages
macrophage secretes IL-12 which interacts with T cell
- T cell secretes IFNgamma which causes pathalogical inflammation and tissue injury
- ROS and NOS
- proteases and cytokines
alternative activation of macrophages?
IL-4 mediated (IL-13 inhitibs classic destructive activation)
- anti-inflamm. effects (IL-10, TGFbeta)
- wound repair, fibrosis (TGFbeta)
look at macrophage feedback charts
do it now!
- look like lymphocytes, but see an area of plasma
- these are activated lymphocytes that are producing antibodies
- these can accumulate in lymph nodes and form tertiary lymphoid organs
difficult to differentiate
- widely distributed in CT
- have receptors for IgE and quickly activated upon binding
- release histamine and prostaglandins
cellular attempt to contain an offending agent
- involves strong activation of T lymphocytes and macrophages
- focus of chronic inflammation consisting of microscopic aggregation of macrphages surrounded by a collar of mononuclear leukocytes, mostly lymphocytes and plasma cells.
- older granulomas have an enclosing rim of fibroblasts and connective tissue
- frequently will see fused eptihelioid cells called giant cells in the periphery
giant cells? two types?
seen in granulomas
= fusion of eptitheliod cells, often located in periphery
1. langhans-type giant cells: small nuclei arranged peripherally around a giant cell
2. foreign body type giant cell: small nuclei arranged haphazardly
presentation of tb
caseating granuloma tubercle
- activated macrophages, rimmed by fibroblasts and occasional langhans giant cells
- central necrosis
what are examples of granulomatous inflammation?
TB (caseating granuloma- caseous necrosis)
what causes fever?
exogenous pyrogens (such as LPS) stimulates leukocytes to release cytokines (IL-1 and TNF: endogenous pyrogens) which increase cyclooxygenases that convert AA to prostaglandins. PGE2 resets the temp to a higher level.
- NSAIDS inhibit fever by inhibit prostaglandin synth.
1. CRP ( upregulated by IL-6) - act as opsonin and binds complement
2. fibrinogen (IL-6) - binds RBC's and they form stacks = erythrocyte sedimentation rate
3. Serum amyloid A (SAA) (upregulated by IL1 and TNF) - acts as opsonin and fixes complement
4. hepcidin: high levels reduce availability of iron, causes anemia with chronic inflammation
increase in blood neutrophil amount
- bacterial infections
increased # of lymphocytes
- seen in viral infections, mono, mumps, measels
bronchial asthma, allergy, parasitic infections
decreased number of WBC's
- seen in cancer, TB and severe alcoholism
- triggered by large amts of of LPS and huge amts of cytokines produced , TNF and IL-1
- activation of coagulation and fibrinolysis
- end organ damage
- cardiac failure, widespread vasodilation (NO production)
- blood clots and bleeding throughout entire body
where do you see neutropenia?
where do you see problems with neutrophils?
- problem with adherence, movement and phagocytizing
where do you phagolysosomal defects?