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GenPath RC Flashcards

1
Q

Where does transmigration of leukocytes occcur?

A

Post capillary venules

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2
Q

What is the function of CD31/PECAM-1 in leukocyte recruitment?

A

Adhesion of leukocytes and migration through interendothelial gaps towards chemical gradient of chemokines

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3
Q

How do leukocytes pierce the basement membrane?

A

Secreting collagenases

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4
Q

What substances act as chemoattractants?

A

Exogenous and endogenous substances

Endogenous: cytokines (IL-8), complement system (C5a), arachidonic acid (AA, mainly leukotrienes B4 - LTB4)

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5
Q

What is the mechanism on how chemoattractant agents function?

A

Chemotactic agents bind to transmembrane G protein-coupled receptors on the surface of leukocytes

Signals from these receptors result in second messengers to be activated that induce polymerization of actin on the leading edge of the cell and localization of myosin filaments at the back

Leading edge of teh leukocyte then extends filopodia that pull back of the cell in teh direction of extension, much as an automobile with front-wheel drice

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6
Q

What cell type does Pseudomonas attract?

A

Neutrophils that are continuously recruited

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7
Q

Describe pathology of leukocyte activation

A

Activation results from signaling pathways that are triggered in leukocytes
—> results in increases in cytosolic Ca and activation of enzymes such as protein kinase C and phospholipase A2

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8
Q

List the main steps of phagocytosis

A
  1. Recognition and attachment of the particle to be ingested by the leukocyte
  2. Engulfement with subsequent formation of a phagocyte vacuole
  3. Killing of the microbe and degradation of the ingested material
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9
Q

List the three types of phagocytic receptors

A
  1. Mannose receptors
  2. Scavenger receptors
  3. Receptors for various opsonins that enable phagocytes to bind/ingest microbes
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10
Q

What is the macrophage mannose receptor?

A

A lectin that binds terminal mannose and fucose residues of glycoproteins and glycolipids

These sugars are typically part of molecules found on microbial cell walls whereas mammalian glycopproteins and glycolipids contain terminal sialic acid or N-acetylgalactosamine (therefore the mannose receptor recognizes microbes and not host cell)

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11
Q

What are scavenger receptors?

A

One of the phagocytic receptors

They bind and mediate endocytosis of oxidized or acetylated low-density lipoprotein (LDL) that do not interact w/ the conventional LDL receptor.

Bind a variety of of microbes in addition to modified LDL particles

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12
Q

What are macrophage integrins?

A

MAC-1 (CD11b/CD18)

Binds microbes for phagocytosis

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13
Q

What enhances phagocytosis of microbes?

A

Opsonins

Microbes are coated with opsonins for which the phagocytes express high-affinity receptors

Major opsonins are :

  1. immunoglobulin G (IgG) antibodies
  2. C3b breakdown product of complement
  3. certain plasma lectins, notably mannnose-binding lectin and collectins, all of which are recognized by specific receptors on leukocytes
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14
Q

What is phagocytosis dependent on?

A

Polymerization of actin filaments

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15
Q

What causes killing of microbes?

A

ROS (reactive oxygen species)

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16
Q

How are ROS produced?

A

Rapid assembly and activation of a multicomponent oxidase, NADPH oxidase (also called phagocyte oxidase), which oxidizes reduced nicotinamide-adenine dinucleotide phosphate (NADPH) and in the process, reduces oxygen to superoxide anion (O2-)

In neutrophils, this is triggered by phagocytosis and is called respiratory burst

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17
Q

How many proteins are in phagocyte oxidase?

A

7

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18
Q

Describe how ROS are produced and act on microbes

A

Activating stimuli –> the cytosolic protein components translcoate to the phagosomal membrane, where they assemble and form the functional enzyme complex

ROS are produced w/in the phagolysosome, where they can act on ingested particles without damaging the host cell

O2-* is converted into H2O2 mostly by spontaneous disputation

H2O2 is not able to kill microbes by itself, the azurophilic granules of neutrophils contain MPO, which in the presence of a halide such as Cl converts H2O2 to HOCL and destroys microbes by halogenation

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19
Q

What are the common antioxidants?

A

Enzyme superoxide dismutase

Catalase (detoxifies H2O2

Glutathione peroxidase

Copper-containing plasma protein ceruloplasmin

Iron-free fraction of plasma transferrin

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20
Q

What is the component of the disease process chronic granulomatous disease?

A

Inherited deficiencies of components of phagocyte oxidase

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21
Q

What are the types of granules in neutrophils?

A

Primary (larger, azurophil)

Secondary (smaller)

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22
Q

What are in primary granules of neutrophils?

A

MPO

Bactericidal proteins (lysozyme, defensins

Acid hydrolases

Neutral proteases (elastase, cathepsin G, nonspecific collagenases, proteinase 3)

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23
Q

What are in secondary granules of neutrophils?

A 
Lysozyme
Collagenase
Gelatinase
Lactoferrin
Plasminogen activator
histaminase
ALP

*lysozyme is in both primary and secondary granules

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24
Q

What are the neutral proteases in neutrophil primary granules?

A

Elastase
Cathepsin G
Nonspecific collagenases
Proteinase 3

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25
Q

What are the functions of acid proteases and neutral proteases?

A

Acid proteases: degrade bacteria and debris w/in phagolysosomes - acidified by membrane-bound proton pumps

Neutral proteases degraded various extracellular components such as collagen, basement membrane, fibrin, elastin, and cartilage —> tissue destruction that accompanies inflammatory processes
…..Neutral proteases can also cleave C3 and C5 complement proteins and release a kinin-like peptide from kininogen

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26
Q

What is the function of neutrophil elastase?

A

Degrade virulence factors of bacteria and thus combat bacterial infections

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27
Q

What types of enzymes do macrophages contain?

A 
Acid hyrdolases
Collagenase
Elastase
Phospholipase
Plasminogen activator
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28
Q

Contrast enzymes in neutrophils and macrophages

A

Both: collagenases, elastase

Macrophages: acid hydrolases, collagenase, elastase, phospholipase, plasminogen activator

Neutrophils

  • Primary: MPO, lysozyme, defensins, acid hydrolases, neutral proteases (elastase, cathepsin G, nonspecific collagenases, proteinase 3)
  • Secondary: lysozyme, collagenase, gelatinase, lactoferrin, plasminogen activator, histaminase, ALP

Additional granules that neutrophils have that macropahges don’t
- MPO, lysozyme, defensins, cathepsin G, proteinase 3, gelatinase lactoferrin, histaminase, ALP
Macrophages have phospholipase that neutrophils do not have

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29
Q

What is the name of an antiproteases to combat the destructive effects of lysosomal enzymes from neutrophils?

A

Alpha1-antitrypsin (major inhibitor of neutrophil elastase)

Alpha2-macroglobulin

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30
Q

What does alpha1-antitrypsin deficiency lead to?

A

Sustained action of leukocyte proteases
—> increased risk of emphysema due to destruction of elastic support fibers in the lung b/c of uncontrolled elastase activity

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31
Q

Function of defensins?

A

These are cationic arginine-rich granule peptides that are toxic to microbes

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32
Q

Function of lysozyme?

A

Hydrolyzes the muramic acid N-acetylglucosamine bond found in the glycopeptide coat of all bacteria

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33
Q

Function of lactoferrin?

A

Iron-binding protein present in specific granules

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34
Q

Function of major basic protein?

A

Is a cationic protein of eosinophils

Limited bactericidal activity, but is cytotoxic to many helminthic parasites

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35
Q

Describe MOA of NET formation

A

Starts with ROS-dependent activation of an arginine deaminase that converts arginines to citrulline
—> leading to chromatin decondensation

MPO and elastase enter the nucleus and cause further chromatin decondensation —> rupture of the nuclear envelope and release of chromatin

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36
Q

Consequence of released nuclear chromatin in NETs?

A

Histones and associated DNA postulated as a source of nuclear antigens in systemic autoimmune diseases (eg lupus)

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37
Q

Role of IL-17 in acute inflammation?

A

Produced by Th17 lymphocytes

Induces secretion of chemokines that recruit other leukocytes

In absence of Th17 cells develop cold abscess (lack warmth/redness)

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38
Q

Mediators involved in termination of acute inflammation

A

Removal of infectious agent cuts off inflammatory mediator production

Switch in type of arachidonic metabolite produced from proinflammatory leukotrienes to antiinflammatory lipoxins and release of antiinflammatory cytokines (TGF-beta, IL-10) from macrophages and other cells

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39
Q

List mediators of acute inflammation

A

Vasoactive amines
Lipid products (prostaglandins and leukotrienes)
Cytokines
Products of complement activation

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40
Q

Histamine source and action?

A

Source: mast cells, basophils, platelets

Action: Vasodilation, increased vascular permeability, endothelial activation

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41
Q

Prostaglandins source and action

A

Source: Mast cells, leukocytes

Action: Vasodilation, pain, fever

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42
Q

Leukotrienes source and action

A

Source: Mast cells, leukocytes

Action: Increased vascular permeability, chemotaxis, leukocyte adhesion and activation

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43
Q

Cytokines (TNF, IL-1, IL-6) source and action

A

Source: macrophages, endothelial cells, mast cells

Action: Local - endothelial actiation (expression of adhesion molecules)
Systemic - fever, metabolic abnormalities, hypotension (shock)

44
Q

Chemokines source and action

A

Source: leukocytes, activated macrophages

Action: Chemotaxis, leukocyte activation

45
Q

Platelet activating factor source and action

A

Source: Leukocytes, mast cells

Action: Vasodilation, increased vascular permeability, leukocyte adhesion, chemotaxis, degranulation, oxidative burst

46
Q

Complement source and action

A

Source: Plasma (produced in liver)

Action: Leukocyte chemotaxis and activation, direct target killing (membrane attack complex), vasodilation (mast cell stimulation )

47
Q

Kinins source and action

A

Source: Plasma (produced in liver)

Action: Increased vascular permeability, smooth muscle contraction, vasodilation, pain

48
Q

List the two major vasoactive amines

A

Histamine

Serotonin

49
Q

What are prostaglandins and leukotrienes produced from?

A

Arachidonic acid that is present in membrane phospholipids

50
Q

What produces prostaglandins?

A

Mast cells
Macrophages
Endothelial cells
..many other types of cells

They are generated by the actions of two cyclooxygenases (COX-1 and COX-2)

51
Q

List the functions of COX-1 and COX-2

A

COX-1 is expressed in most tissues, may serve various homeostatic functions (e.g. fluid and electrolyte balance in the kidneys, cytoprotection in the gastrointestinal tract) and is also induced by inflammatory stimuli

COX-2 expression is mainly confined to cells that are participating in inflammatory reactions

52
Q

List the functions of the prostaglandins by individual type

A

TxA2 causes vasoconstriction, promotes platelet aggregation

PGI2 (prostacyclin) and stable end product PGF1a causes vasodilation, inhibits platelet aggregation

PGD2/PGE2 causes vasodilation and increases permeability of postcapillary venules –> potentiating edema formation
PGD2 is also a chemoattractant for neutrophils

53
Q

Describe leukotrienes - where produced, function, types

A

Produced in leukocytes and mast cells by the action of lipooxygenase

Function: involved in vascular and smooth muscle reactions and leukocyte recruitment

Types: (1) 5-lipoxygenase (predominate in neutrophils, chemoattractant for neutrophils)

(2) LTB4 is a potent chemotactic agent and activator of neutrophils, causing aggregation/adhesion of the cells to venular endothelium, generation of ROS, and release of lysosomal enzymes
(3) Cysteinyl-containing leukotrienes LTC4, LTD4, LTE4 = intense vaoconstrictio, bronchospasm, increased permeability of venules

leukotrienes are more potent than histamine in increasing vascular permeability and causing bronchospasm

54
Q

Function of lipoxins?

A

Also generated from AA by lipoxygenase pathway, but unlike prostaglandins and leukotrienes…lipoxins suppress inflammation by inhibiting neutrophil chemotaxis and adhesion to endothelium

**also two cell populations are needed for transcellular biosynthesis of these mediators (neutrophils synthesize precursors of active lipoxins and pass these to platelets, where they are converted to mature lipoxins)

55
Q

How do TNF and IL-1 play a role in leukocyte recruitment?

A

Promote adhesion of leukocytes to endothelium and their migration through blood vessels

56
Q

How many groups of chemokines are they and how are they named?

A

4 groups of chemokines

C-X-C - have 1 amino acid residue separating the first 2 of 4 conserved cysteine residues
C - C - first 2 conserved cysteine residues adjacent
C chemokines lack the first and third of 4 conserved cysteines
CX3C contain 3 amino acids between the two cysteines

57
Q

What are in the C-X-C chemokine group?

A

IL-8 (CXCL8) is secreted by activated macrophages, endothelial cells, other cells

Limited activity on monocytes and eosinophils (mainly affects neutrophils)
Most important inducers are microbial products, IL-1 and TNF

58
Q

What are in the C-C chemokine group?

A

Monocyte chemoattactant protein (MCP-1, CCL2)
Eotaxin (CCL11)
Macrophage inflammatory protein 1a (MIP-1a, CCL3)

eotaxin selectively recruits eosinophils

59
Q

What are in the C chemokine group?

A

Lymphotactin, XCL1 are specific for lymphocytes

60
Q

CX3C chemokine group?

A

Fractalkine (CX3CL1)

Exists in 2 forms (1) cell surface bound protein induced on endothelial cells by inflammatory ctokines that promotes strong adhesion of monocytes and T cells (2) soluble form derived by proteolysis of the membrane-bound protein that has potent chemoattractant activity for the same cell

61
Q

Where are IL-6 and IL-17 produced?

A

IL-6 is made by macrophages and other cells

IL-17 produced mainly by T lymphocytes

62
Q

What is the critical step in the complement system?

A

Proteolysis of the third (and most abundant) component, C3

63
Q

Cleavage of C3 can occur by one of three pathways

A

Classical Pathway - triggered by binding of C1 to antibody (IgM or IgG) that has combined with antigen

Alternative pathway can be triggered by microbial surface molecules (e.g. endotoxin or LPS, complex polysaccharides, cobra venom, and other substances in the absence of antibody)

Lectin pathway in which plasma mannose-binding lectin binds to carbohydrates on microbes and directly activated C1

64
Q

All three pathways of complement activation lead to….

A

Formation of an active enzyme called C3 convertase, which splits C3 into two functionally distinct fragments, C3a and C3b

C3a is released
C3b becomes covalently attached to the cell/molecule and C3b binds to previously generated fragments forming C5 convertase

C5 convertase cleaves C5 to release C5a and leave C5b attached to the cell surface
C5b binds the late components C6-C9 culminating in the formation of the membrane attack complex (composed of multiple C9 molecules)

65
Q

List the 3 functions of complement

A

Inflammation
Opsonization and phagocytosis
Cell lysis

66
Q

List the details of the inflammation function of complement

A

C5a, C3a and to lesser extent, C4a are cleavage products of the corresponding complement components that stimulate histamine release from mast cells and thereby increase vascular permeability and cause vasodilation

These are called anaphylatoxins b/c they have similar effects to those of mast cell mediators that are involved in the reaction called anaphylaxis

67
Q

C5a function?

A

Involved in development of MAC

C5a also a chemotactic agent for neutrophils, monocytes, eosinophils, and basophils

C5a activates the lipoxygenase pathway for AA metabolism in neutrophils and monocytes –> further release of inflammatory mediators

68
Q

Describe the function of opsonization and phagocytosis in complement

A

C3b and its cleavage product inactive C3b (iC3b) when fixed to a microbial cell wall, act as opsonins and promote phagocytosis by neutrophils and macrophages, which bear cell surface receptors for the complement fragments

69
Q

Describe the cell lysis pathway of complement

A

MAC on cells makes these cells permeable to water and ions –> this results in osmotic lysis of the cells

MAC process kills microbes w/ thin cell walls (e.g. Neisseria bacteria)

70
Q

What controls/inactivates complement?

A

Cell-associated and circulating regulatory proteins

C1 inhibitor (C1 INH)
Decay accelerating factor and CD59
Complement Factor H

71
Q

Describe C1 inhibitor

A

C1 inhibitor (C1 INH) blocks activation of C1 (first protein of the classical complement pathway). Inherited deficiency of this inhibitor causes hereditary angioedema

**one of the inhibitors of the complement pathway

72
Q

Describe decay accelerating factor (DAF) and CD59

A

Two proteins linked to plasma membranes by a glycophosphatidylinositol (GPI) anchor

DAF precents formation of C3 convertase
CD59 inhibits formation of the MAC

73
Q

Describe Complement Factor H

A

Circulating glycoprotein that inhibits the alternative pathway of complement activation by promoting the cleavage and destruction of C3b and the turnover of the C3 convertase

74
Q

Function of Platelet-Activating Factor (PAF)

A

Phospholipid-derived mediator that is elaborated by platelets, basophils, mast cells, neutrophils, macrophages, and endothelial cells

Function: platelet aggregation, vasoconstriction, bronchoconstriction
**at low concentrations (vasodilation and increased venular permeability)

75
Q

What supports the link between inflammation and coagulation?

A

Protease-activated receptors (PAR)

76
Q

Protease-activated receptors (PAR)

A

On leukocytes

Activated by thrombin (the protease that cleaves fibrinogen to produce fibrin, which forms the clot)

PARs platelet activation

77
Q

What are Kinins?

A

Kinins are vasoactive peptides derived from plasma proteins, called kininogens by specific proteases called kallikreins

eg. Bradykinin

78
Q

Function of Bradykinin

A

Increases vascular permeability and cause contraction of smooth muscle, dilation of blood vessels, and pain when injected into the skin

Short-lived action as they are inactivated quickly by kiniase
Implicated in some forms of anaphylaxis

79
Q

List a few neuropeptides

A

Substance P

Neurokinin A

80
Q

Function of neuropeptides?

A

(e.g. Substance P and neurokinin A)

Secreted by sensory nerves and various leukocytes

Initiation and regulation of inflammatory response

81
Q

Which mediators help with “cross-talk” between the nervous system and immune/inflammatory reactions?

A

Neuropeptides (receptors expressed on leukocyte)

(E.g. activation of the efferent vagus nerve inhibits the production of proinflammatory cytokines such as TNF, providing a mechanism for suppressing inflammation)

82
Q

List the morphologic features of acute inflammation and chronic inflammation

A

Acute inflammation: vascular changes, edema, neutrophilic infiltration

Chronic inflammation: infiltration w/ mononuclear cells (macrophages, lymphocytes, plasma cells); tissue destruction, attempts at healing (by connective tissue replacement of damaged tissue, angiogenesis, fibrosis)

83
Q

Compare/contrast classically and alternatively activated macrophages

A

Classical: indued by microbial products (e.g. endotoxin) produce NO and lysosomal enzymes. Main role is host defense to destroy microbes and promote the inflammatory response (cytokines produced: IL1, IL12, IL23, chemokines)

Alternative: Induced by cytokines other than IFN-gamma (IL4, IL13 produced by lymphs/other cells). Macrophages are not actively microbicidal, instead their principle function are to terminate inflammation and promote tissue repair

84
Q

Describe the role of lymphocytes in chronic inflammation

A

Microbes and other environmental antigens activate T and B lymphocytes —> which amplify and propagate chronic inflammation

**lymphocytes may be the dominant population in the chronic inflammation seen in various autoimmune diseases

CD4+ T lymphocytes promote inflammation and influence the nature of inflammatory reactions

85
Q

List and describe the 3 subsets of CD4+ T lymphocytes

A

Th1 cells produce the cytokine IFN-gamma, which activates macrophages in the classical pathway

Th2 cells secreted IL-4, IL-5, and IL-13 which recruit and activated eosinophils and are responsiple for the alternative pathway of macrophage activation

Th17 cells secrete IL-17 and other cytokines, which induce the secretion of chemokines responsible for recruiting neutrophils (and monocytes) into the reaction

86
Q

Describe which areas of defense the 3 CD4+ T cells are involved in

A

Th1 and Th17 are involved in defense against many types of bacteria and viruses and in autoimmune diseases in which tissue injury is caused by chronic inflammation

Th2 defense against helminthic parasites and in allergic inflammation

87
Q

What cytokines stimulate an acute phase reaction ?

A

TNF
IL-1
IL-6

Others such as interferons also contribute

88
Q

Describe what happens w/ an acute phase reaction?

A

Fever (cytokines - TNF, IL-1 stimulate production of prostaglandins in hypothalamus)
Elevated levels of acute phase proteins
Leukocytosis
SIRS

89
Q

What induces fever?

A 
IL-1 and TNF
Bacterial products (exogenous pyrogens, eg LPS)

Prostaglandins (esp PGE2) stimulate production of neurotransmitters by the hypothalamus that reset the body’s steady-state temperature to a higher level
NSAIDs work by inhibiting prostaglanding synthesis

90
Q

List acute phase proteins

A

C-reactive protein (CRP)
Fibrinogen
Serum amyloid A (SAA)

Others: Hepcidin and Thrombopoietin

91
Q

How does inflammation cause rouleaux?

A

Fibrinogen binds to RBCs and causes them to form stacks (rouleaux) that sediment more rapidly at unit gravity than do individual RBC

92
Q

Function of Hepcidin?

A

Small protein that reduces the availability of iron to erythroid progenitors in the bone marrow; over tie, this effect may lead to anemia of chronic inflammation

Is an acute phase protein and released in increased amounts w/ inflammation

93
Q

Function of Thrombopoietin

A

Major growth factor for megakaryocytes int eh bone marrow, is upregulated and as a result of systemic inflammation may be associated with an elevated platelet count

94
Q

Which cytokines are responsible for marked leukocytosis (leukemoid reaction) w/ inflammation?

A

TNF

IL-1

95
Q

Which cytokines are involved in hepatocyte regneration?

A

Hepatocyte growth factor
TGF-alpha

IL-6 (produced by Kupfer cells)

Stop signals poorly known (suspect TGF-beta)

96
Q

Describe the mechanism of angiogenesis

A

VEGFs (mainly VEGF-A stimulate migration/proliferation of endothelial cells –> capillary sprouting), promotes vasodilation by production of NO

FGFs (fibroblast growth factors, mainly FGF-2) stimulate proliferation of endothelial cells and promote the migration of macrophages and fibroblsts to the damaged area and stimulate epithelial cell migration

Angiopoietins 1 and 2 are growth factors –> angiogenesis

Newly formed vessels stabilized by pericytes and smooth muscle and deposition of connective tissue

PDGF and TGF-beta stabilize

97
Q

What is notch signaling?

A

Regulates the sprouting and branching of new vessels and thus ensures that the new vessels are formed and have proper spacing to effectively supply the healing tissues with blood

98
Q

Mechanism of laying down connective tissue

A
  1. Migration and proliferation of fibroblasts to site of injury
  2. Deposition of ECM proteins produced by these cells

processes orchestrated by PDGF, FGF-2, TGF-beta and the major sources of these factors are inflammatory cells (particularly alternatively activated M2 macrophages

99
Q

What is the most important cytokine for the synthesis and deposition of connective tissue proteins

A

TGF-beta

**produced by most cells in granulation tissue (esp alternatively activated macrophages)

100
Q

Describe MOA of remodeling of connective tissue

A

MMPs degrade collagens and other ECM components

- MMPs = matrix metalloproteinases (so called b/c they are dependent on metal ions (e.g zinc) for their activity

101
Q

List factors that may influence tissue repair

A 
Infection
Diabetes
Nutritional status
Glucocorticoids 
Mechanical factors
Poor perfusion
Foreign bodies
Type/extent ot tissue injury
Location of the injury
102
Q

How do glucorticoids contribute to weakened scar formation?

A

Glucorticoids inhibit TGF-beta production and diminished fibrosis (although this is often wanted in ocular injuries to reduce scar formation)

103
Q

PDGF fxn?

A

Stimulates mitogenesis of smooth muscle and fibroblasts

104
Q

FGF (fibroblast growth factor)

A

Stimulates fibroblast proliferation

105
Q

Transforming growth factor-beta (TGF-beta)

A

Modulates vascular repair by inhibition of proliferation of various cell types, including endothelium

106
Q

Increased/upregulation of p16 results in?

A

More through teh growth cycle

Proliferation or neoplasia

GenPath (9 decks)

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