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1. Inflammation
Marc Imhotep Cray, M.D.
Basic Medical Sciences Teacher
http://www.imhotepvirtualmedsch.com/
Companion Inflammation Notes

2. Inflammation
2

3. Inflammation
Definition
EVOLUTION OF
“Inflammation is a complex reaction of
INFLAMMATION
a tissue and its microcirculation to a
pathogenic insult. It is characterized • Engulfment/entrapment
by the generation of inflammatory
mediators and movement of fluid & • Neutralization of irritant
• Elimination of injurious
leukocytes from the blood into
extravascular tissues.”
agent
3

4. The inflammatory response:
• Is fundamentally a protective/defensive
response
• Persists until the inciting stimulus is removed
and the mediators are dissipated or inhibited
• Can be potentially harmful:
– Anaphylactic shock (peanut allergy)
– Systemic inflammatory response syndrome
(SIRS)
• Is closely intertwined with repair
• Therapeutic strategies target critical control
points in inflammatory pathways
4

5. Acute Inflammation: major
components
• Vascular changes:
– Vasodilation and increased blood flow
– Increased vascular permeability
• Cellular events:
– Leucocyte transmigration
– Phagocytosis
• Chemical mediators
(acute & chronic)
5

6. Inflammation: the players
6

7. Cardinal Signs
(Celsus, 2 AD)
•
•
•
•
•
Redness (rubor)
Swelling (tumor)
Heat (calor)
Pain (dolor)
Loss of function (functio laesa)
(the fifth cardinal sign added by Virchow)
7

8. Inflammation
Cardinal Signs
Patient with a Methicillin-resistant Staphylococcus aureus
wound infection, and classic signs of inflammation.
8

9. Inflammation
Cardinal Signs
X-ray of previous patient showing non-union of fracture.
Holes are from orthopedic screws.
9

10. Inflammation
Cardinal Signs
Bone scan of same patient, showing uptake in
area of active inflammation.
10

11. Acute Inflammation:
1. Vasodilation/increased
blood flow
2. Deposition of fibrin and
other plasma proteins
(exudate)
3. Transmigration and
accumulation of
neutrophils
11

12. •
Vasodilation
•
Slowing of
circulation
•
Stasis and
margination
12

13. Inflammation
Stasis and Margination
Polymorphs at margin of a vessel in acutely inflamed tissue.
13

14. Vascular Leakage:
Transudate: (edema)
specific gravity <1.015 and
protein
content low
Exudate: (inflammation)
specific gravity >1.015 and
protein
content high
14

15. Vascular Leakage
(cont.)
Rat model:
only venules leak and
deposit carbon
15

16. Leukocyte Extravasation and
Phagocytosis
• Margination, rolling,
activation and adhesion
• Transmigration
(diapedesis)
• Migration toward the
site of injury along a
chemokine gradient
16

17. Adhesion Molecule Modulation
• P-selectin is redistributed
to the cell surface from
the Weibel-Palade bodies
due to stimulation by
thrombin, histamine,
and Platelet Activating
Factor (PAF)
17

18. Adhesion Molecule Modulation
• Induction of E-selectin
on endothelium by IL1 and TNF
• Increased avidity of
binding of integrins
(conformational
change)
18

19. Endothelial/Leukocyte Adhesion
Molecules: Summary
19

20. Animation
20

21. 21

22. 22

23. Sequence following acute injury:
23

24. Mechanisms of Inflammatory Cell
Function
•
The formation of a ligand-receptor
complex leads to activation of a specific
phospho-diesterase (phospholipase C)
in the plasma membrane (stimulusresponse coupling)
•
•
•
Increased phospholipid metabolism
Increased intracellular calcium
Activation of protein kinases and
phosphatases
24

25. Biochemical Events in Leucocyte Activation
25

26. Chemotaxis
• Locomotion along a
chemical gradient
• Chemoattractants:
Exogenous (from
bacteria)
Endogenous (from
mediators)
26

27. Chemotaxis
• Exogenous mediators, e.g.:
– N-formyl methionine terminal amino acids
from bacteria
– Lipids from destroyed or damaged
membranes (including LPS)
• Endogenous mediators, e.g.:
– Complement proteins (C5a)
– Chemokines, particularly IL-8
– Arachidonic acid products (LTB4)
27

28. Phagocytosis
• Recognition and
attachment
• Engulfment
• Degradation (killing)
28

29. Bactericidal activity
•
Activated oxygen species
•
•
•
Superoxide (.O2) - formed via NADPH
oxidase
Hydrogen peroxide (H2O2) - formed via
spontaneous dismutation of superoxide)
Hypochlorous acid (HOCl) (Myeloperoxidase)
Probably the primary bactericidal agent in
neutrophils
• Myeloperoxidase converts H2O2 into HOCl.
.
• Hydroxl radical ( OH)
•
29

30. Bactericidal activity
•
Non-oxidative bacterial killing
•
•
•
•
•
•
Lysosomal hydrolases (1o and 2o granules)
Bactericidal/permeability-increasing protein
(1o granules - affects Gram-negatives)
Defensins (1o granules)
Lactoferrin (2o granules - chelates iron)
Lysozyme (1o and 2o granules, lysosomes)
Bactericidal proteins of eosinophils
30

31. Tissue Injury by Inflammatory
Cells
"Our arsenals for fighting off bacteria are so
powerful, and involve so many different
defense mechanisms, that we are more in
danger from them than from the invaders.
We live in the midst of explosive devices;
we are mined."
– Lewis Thomas
31

32. Tissue Injury by Inflammatory
Cells
•
Activated oxygen species
•
•
•
•
•
Can migrate through intact plasma
membranes
Initiate lipid peroxidation
React with DNA
Oxidize sulfhydryl groups of proteins
Degrade extracellular matrix components
32

33. Tissue Injury by Inflammatory
Cells
•
Lysosomal enzymes
•
•
Since these enzymes are used to degrade
microorganisms in lysosomes, obviously
they could damage tissue in the
extracellular environment
Usually protease activity is controlled by a
variety of anti-proteases present in plasma
( 1-anti-trypsin, 2-macroglobulin, etc.)
33

34. Tissue Injury by Inflammatory
Cells
•
Phagocytic cell adherence
•
Adherence to basement membranes, other
components of the extracellular matrix and
other cells by phagocytes enhances the
damage caused by reactive oxygen
species and lysozyme, because normal
inhibitors present in plasma cannot gain
access to that space by virtue of the
phagocytic cell adherence
34

35. Tissue Injury by Inflammatory Cells
Abscess, formed via
liquifactive necrosis,
primarily due to the action of
neutrophils.
35

36. Tissue Injury by Inflammatory Cells
Normal glomerulus, containing 50-100 nuclei.
36

37. Tissue Injury by Inflammatory Cells
• Post-streptococcal
glomerulonephritis,
showing a hypercellular
glomerulus.
• Most of the extra cells
are neutrophils, reacting
with immune complexes
in the glomerular
basement membrane.
• This is a very bad thing
for the glomerulus, and it
is usually destroyed and
heals with a hyaline
scar.
37

38. Clinical examples of
leukocyte-induced injury
38

39. Defects in Phagocytosis
•
Congenital
•
Chediak-Higashi Syndrome
(autosomal recessive)
•
•
•
Job Syndrome (Hyper IgE)
Chronic granulomatous disease
(x-linked)
•
•
•
Defective intracellular transport
protein, inability to lyse bacteria
No oxidative burst
Myeloperoxidase deficiency
Acquired
•
•
•
•
•
Iatrogenic immunosuppression
(most common)
Overwhelming infections
Severe trauma or burn
Diabetes mellitus
Chronic debilitating disease
39

40. Summary of Acute
Inflammation
What You MUST Known
40

41. Chemical Mediators of
Inflammation
• Originate from either plasma or cells
• Bind to specific cellular receptors, have direct
enzymatic activity or mediate oxidative damage
• One mediator can stimulate release of additional
mediators (“amplification”)
• Effects on multiple cell types, varying effects on
different cells
• Once activated and released …are short-lived
• Have potential to cause harmful effects
41

42. Sources of Inflammatory Mediators
• Cell-derived:
– Proteins sequestered in granules
– Membrane phospholipids (via
arachidonic acid metabolism)
– Vasoactive amines (mast cells and
platelets)
• Inactive precursors in plasma:
– Complement proteins (C3a, C5a)
– Coagulation proteins initiated by
Hageman factor (FDPs)
42

43. Chemical mediators of
inflammation
43

44. Chemical mediators of
inflammation
• Vasoactive amines:
– Histamine
– Serotonin
• Plasma proteases:
– Complement system
– Kinin system
– Coagulation system
• Arachidonic acid
metabolites:
– Prostaglandins
– Leukotrienes
– Lipoxins
• Platelet activating factor
• Cytokines and
chemokines
• Nitric oxide
• Leucocyte lysosomal
consituents
• Oxygen-derived free
radicals
• Neuropeptides
44

45. 45

46. Vasoactive Amines
•
Histamine:
– Source = mast cell granules
– Wide distribution around vessels
– Main action is vasodilation and increased
vascular permeability
– Released by trauma, heat or cold,
complement, cytokines
– G-protein-coupled receptor
•
Serotonin (5-hydroxytryptamine):
– Source = platelet granules
– Actions similar to histamine
– Released by platelet aggregation (collagen,
thrombin, ADP, PAF from mast cells
– G-protein-coupled receptor
46

47. Plasma Protease Systems
• Complement, coagulation, fibrinolytic
and kinin systems
• All zymogen-based proteolytic cascades
with great amplification characteristics
• Generate pro-inflammatory by-products
• Mutual interactions between systems
47

48. Chemical Mediators: proteases
•
Complement cascade system
– Classic and alternative pathways
• C3 is the critical control point, and interacts with both pathways
• C3a and C5a are known as “anaphylatoxins”, and are capable of
releasing histamine from mast cells, along with potent chemotactic
abilities (C5a)
• Membrane attack complex (MAC) is the active agent of complement
lysis and consists of C5-9
48

49. Biologic effects of complement
fragments
• Vascular phenomena:
– Increase vascular permeability
– Vasodilation
• Leucocyte adhesion, chemotaxis:
C5a
• Phagocytosis: C3b and C3bi
– Opsonins
49

50. Complement: regulatory
mechanisms
• Regulation of C3 and C5 convertases:
– Decay acceleration and proteolysis
• Binding of activated complement
components:
– C1 inhibitor
– CD59 membrane inhibitor of lysis
50

51. Chemical Mediators: proteases
• Kinin system
– Vasoactive peptides called kinins are
generated by proteases called
kallikrein
– Hageman factor is a potent activator
of kallikrein
– Most important product is bradykinin
• Pain + vascular dilation
• Coagulation/Fibrinolytic
pathway
– Both systems are induced by
activated factor XIIa (Hageman)
– The coagulation and fibrinolytic
systems complement and
counterbalance each other
– Most important molecules are
fibrinogen, fibrin, thrombin,
plasminogen, and plasmin
51

52. Arachidonic Acid Metabolites
• Arachidonic acid (AA) is
a 20-C polyunsaturated
fatty acid released from
membrane phospholipids
by phospholipase A2
• Mechanical, chemical
physical stimuli can
activate phospholipase A2
• Metabolites of AA are
called eicosanoids, and
are generated by
cyclooxygenases and
lipoxygenases
• Cycloxygensases
synthesize prostaglandins
and thromboxane
• Lipoxygenases synthesize
leukotrienes and lipoxins
• Eicosanoid receptors are
G-protein-coupled
transmembrane proteins
• Eicosanoids mediate all
aspects of inflammation
52

53. Chemical Mediators of Inflammation
•
Arachidonic acid metabolites
– Synthesized from cell membrane phospholipids though the action of phospho-lipases
(inhibited by corticosteroids)
– Form leukotrienes via 5-lipoxygenase
– Form prostaglandins and thromboxane A2 via cyclo-oxygenase (COX-1 inhibited by
aspirin and indomethacin, COX-2 inhibitors now coming on the market)
53

54. Inflammatory Action of Eicosanoids
54

55. 55

56. Chemical Mediators of Inflammation
• Platelet activating
factor
– Numerous effects,
including
vasodilation and
increased
vascular
permeability, with
100-10,000-fold
increased activity,
with respect to
those actions,
when compared to
histamine
56

57. Chemical Mediators of Inflammation
• Cytokines of importance
– Interleukin 1- endothelial cell activation
– Interleukin 2 (T cell growth factor)
– Tumor necrosis factor
cachectin)
– Tumor necrosis factor (lymphotoxin)
– Various colony stimulating factors, named
for the stem cell they affect
– Chemokines – important in chemotaxis
57

58. Cytokines mediating inflammation
• Tumor necrosis
factor
• Interleukin-1 (IL-1)
• Chemokines
58

59. Inflammatory Cells and their
Chemokines
59

60. Chemical Mediators of Inflammation
• Nitric oxide (NO)
– Formed by NO synthase (NOS)
• Constitutively expressed in endothelial and
neuronal cells. May be increased rapidly by calcium
influx.
• Inducible NOS – induced in macrophages by TNFor IFN-
– Potent vasodilator
– Involved in the pathogenesis of septic shock
60

61. 61

62. Inflammation
Neutrophil Granules
•
•
•
Primary - contain serine proteases,
lysozyme and phospholipase A2
Secondary - similar to primary, but also
contain lactoferrin and collagenase
Tertiary - present at the leading edge of
migrating PMNs, contain gelatinases
that are capable of degrading basement
membrane
62

63. Inflammation
Neutrophil Granules
63

64. Mediators of Inflammation
64

65. Mediators of Inflammation
65

66. Outcomes of Acute Inflammation
• Resolution (the hoped-for result)
• Abscess (via liquifactive necrosis)
• Scar (sometimes occurs even if pathogen is
eliminated)
• Persistent inflammation (chronic
inflammation) – due to a failure to completely
eliminate the pathological insult (injury)
66

67. Resolution of acute
inflammation
• Return to normal vascular
permeability
• Drainage of edema fluid
into lymphatics or
pinocytosis into
macrophages
• Phagocytosis of apoptotic
neutrophils and necrotic
debris by macrophages
• Disposal of macrophages
67

68. Chronic Inflammation
•
•
•
Inflammation of prolonged duration
(weeks, months)
Active inflammation, tissue destruction
and attempts at repair proceed
simultaneously
Settings:
•
•
•
Persistent infection
Prolonged exposure to toxic agent
Autoimmunity
68

69. Chronic Inflammation
• Histologic features
– Infiltration by mononuclear cells:
macrophages, lymphocytes, and plasma
cells
– Tissue destruction by ongoing
inflammation
– Attempts at healing, including
angiogenesis, fibroblasts and fibrosis
69

70. Chronic Inflammation: Lung
• Collection of chronic
inflammatory cells
• Destruction of
parenchyma
• Replacement by
connective tissue
(fibrosis)
70

71. Maturation of
macrophages
From Abbas et al Cellular and Molecular Immunology 1997
71

72. Macrophage activation
• Via cytokines from
immune-activated Tcells
• By non-immunologic
stimuli: endotoxin,
fibronectin, mediators
72

73. Macrophage accumulation
73

74. Chronic Inflammation
• Monocyte/Macrophages
– Key cell in chronic and granulomatous
inflammation
– Reproduce locally, at the site of injury
– Produce numerous cytokines, which
continue to recruit additional cells,
including more macrophages
– May present antigen to T-cells, producing
specific hypersensitivity reactions
74

75. Chronic Inflammation
Products released from macrophages
75

76. Lymphocyte-macrophage
interactions
• Activated lymphocytes
and macrophages
influence each other
• Release mediators that
affect other cells
76

77. Chronic Inflammation: other cells
• Plasma cells
(lymphocytes)
• Mast cells
• Eosinophils
77

78. Granulomatous
Inflammation
•
•
•
Distinct pattern of chronic inflammation
in which the chief reactive cell is an
activated macrophage
Destruction of tissue is primarily via the
action of killer T cells (CD8+), directed by
macrophages
Hence, the old term for tuberculosis was
consumption, for good reason
78

79. Examples of
Granulomatous Inflammation
79

80. Granulomatous Inflammation
• Tuberculous lung, showing massive destruction by granulomatous inflammation.
• This type of response is simply the best the body can do, since the inciting
organism cannot be removed. Mycobacteria may live for years, perhaps even a
80
lifetime, within granulomas.

81. Granulomatous Inflammation
• Characteristic arrangement of cells in a granuloma.
• The extracellular matrix is active in orchestrating the precise alignment of cells.
• Granulomas often form when indigestible substances are present, such as
foreign bodies, or Mycobacteria, which are resistant to oxidative killing.
Fibroblasts
Lymphocytes
Macrophages, Epithelioid
Cells, and Giant Cells
Caseous Necrosis
Non-caseating
Granuloma
Caseating Granuloma
81

82. Granulomatous Inflammation
• Granuloma, H&E, showing Langhans giant cells.
• These multinucleated cells have macrophage markers on their cell surface,
and are apparently the result of fusion of individual macrophages. While
useful in diagnosing a granuloma, they are not considered the characteristic
cell.
• That honor belongs to the epitheliod histiocyte, which also has macrophage
cell surface markers.
82

83. Granulomatous
Inflammation
• Granuloma, H&E, showing
Langhans giant cells.
• These multinucleated cells have
macrophage markers on their cell
surface, and are apparently the
result of fusion of individual
macrophages.
• While useful in diagnosing a
granuloma, they are not
considered the characteristic cell.
• That honor belongs to the
epitheliod histiocyte, which also
has macrophage cell surface
markers.
83

84. Tissue morphology: serous
inflammation
84

85. Tissue morphology: fibrinous
inflammation
85

86. Tissue morphology: suppurative
inflammation
86

87. Tissue morphology: inflammation
exudative peptic ulceration
Esophagus
Stomach
87

88. Systemic Manifestations of
Inflammation
•
•
•
•
Systemic effects can be seen in setting of acute
or chronic inflammation
Largely mediated by cytokines
Fever - clinical hallmark of inflammation
• Endogenous pyrogens: IL-1 and TNFLeukocytosis:
neutrophils bacterial (pneumonia)
lymphocytes viral (infectious mono)
eosinophils parasites, allergy
•
Acute phase reactants - non-specific elevation
of many serum proteins - will markedly increase
the “sed rate”
88

89. Acute phase response
• Acute phase proteins:
a group of proteins - CRP, mannose-binding
protein, SAA, … that modulate inflammation
(complement cascade, stimulate chemotaxis
of phagocytes)
• Inflammatory cytokines (TNF, IL-1, )
stimulate liver cells to sythesize acute phase
proteins
• Acute phase response provides an early
defense before full activation of immune
responses
89

90. Acute phase reaction
• Endocrine/metabolic:
C-reactive protein (CRP)
Serum amyloid A (SAA)
Serum amyloid P (SAP)
• Autonomic: blood flow
• Physiologic/behavioral
(shivering)
90

91. Systemic Manifestations of
Inflammation
•
Shock – most common in Gram-negative
septicemia (bacteria in the bloodstream),
although it can occur with Gram-positive
bacteremia
•
•
Lipopolysaccharide (LPS or endotoxin) of
Gram-negatives can produce symptoms of
shock when injected into animals
TNF- can produce a similar syndrome
91

92. 92

93. Systemic Manifestations of
Inflammation
•
•
•
Therapy for fever and inflammation
targets arachidonic acid metabolism
(aspirin)
Therapy for shock focuses on fluid
resuscitation, and proper selection of
antibiotics (more to come later)
Experimental therapy for shock using
anti-TNF- , and other antibodies directed
against cytokines, has, so far, failed to
improve survival
93

94. THE END
THANK YOU
Reference:
Kumar et al. Robbins and Cotran’s Pathological Basis of Disease 8th
edition, Elsevier 2010
Learn more, WebPath
• Inflammation:
75 Images
Patterns of cellular and tissue injury with inflammation,
including acute, chronic, and granulomatous inflammation.
• Medical Pathology - What's an Acute Inflammation?
(National Institute of Health) Video
94