Macrophages are derived from bone marrow monocytes. Three major tissue macrophages are: 1. Kupffer cells (liver) 2. Alveolar macrophages (lungs) 3. Microglia (CNS) Two major methods of macrophage activation are: 1. Classical activation (M1): Activated by IFN-γ and LPS. Produce inflammatory cytokines. 2. Alternative activation (M2): Activated by IL-4/IL-13. Produce anti-inflammatory mediators and promote tissue remodeling.

1. Inflammation
and Repair
AHD presentation
November 2015
Mahra Nourbakhsh

2. Definition
• A response of vascularized tissues to infections and
damaged tissues that brings cells and molecules of host
defense from the circulation to the sites where they are
needed, in order to eliminate the offending agents.
• The Purpose:
o To get rid of initial cause of injury
o To get rid of consequences of such injury

3. Historical Aspects
• Celsus a Roman writer:
1. Rubor: Redness
2. Tumor: Swelling
3. Color: Heat
4. Dolor: Pain
• Virchow:
5. Functio Laesa: Loss of function

4. Inflammation: Useful VS.
Harmful
• Protective but may be the cause of
diseases:
1. Misdirected reaction:
• Autoimmune
2. Inadequate reaction:
• Hypersensitivity reactions type I to IV
3. Chronic reaction
• Fibrosis: pulmonary, cirrhosis, constrictive
pericarditis.

5. Injurious Agents
(Causes of Inflammation)
• Infection: Viral, bacterial, fungal, parasites or toxins
• Tissue Necrosis: Ischemia, trauma, physical and
chemical injuries.
• Foreign Bodies: Urate crystals, cholesterol crystals,
lipids.
• Immune Reactions: Hypersensitivity syndromes.

6. Sequential Steps of Typical
inflammatory reaction
• Recognition of offending agents.
• Recruitment of leukocytes and plasma protein to the site
of injury.
• Elimination of the offending agents by activated
leukocytes and proteins.
• Control and termination of the inflammatory reaction.
• Damages tissue is repaired.

7. Inflammation: Acute VS.
Chronic
Feature Acute Chronic
Onset Fast: minutes or hours Slow: days
Cellular infiltrate Mainly neutrophils
Monocytes/macrophages
and lymphocytes
Tissue injury,
fibrosis
Usually mild and self-
limited
Often severe and
progressive
Local and
systemic signs
Prominent Less
Innate Adaptive?

8. Question
How a pathogen is recognized by innate immune system? Is
there a specific structure or pattern?
If yes bring two examples

9. Recognition of
offending agents
• Specific molecular pattern on offending agents help to
recognize the pathogens; Pathogen Associated
Molecular Pattern (PAMP):
1. Lipopolysacharides (LPS) on gram negatives
2. Lipoteicoic acids on gram positives
3. Flagellin on bacteria
4. Unmethylated CpG
5. Ds RNA in viruses.

10. Recognition of offending agents
• Sensing the presence of foreign invaders: Pattern
Recognition Receptors (PRRs)
1. Membrane bounds (plasma membrane and endosomes) receptors: Toll-Like Receptors
(TLRs), C-Type Lectin Receptors (CLRs)
2. Cytosolic Receptors: NOD-Like Receptors (NLRs)
• Sensing the cell damage: activation of
inflammasomes and production of IL-1
1. Mitochondria damage: ATP
2. Break down of DNA : Uric acids
3. Damage to Na+/ K+ pump: Increased intracellular K+
4. DNA fragments: DNA damage response, Ataxia Telangiectasia Mutated (ATM) and ATM
RAD3-Related (ATR) kinases
• Leukocytes Receptors for FC tail of antibodies and
C3b of complement system: Opsonization
• Circulating proteins: Complement system, Mannose-
binding lectins and collectins

11. Question
Which cells from innate immune system are able to recognize
the foreign invaders?
How do they activate the remainder of the innate system?

12. Recognition of offending agents
(Cells and Chemicals)
• Cells:
1. Tissue Macrophages
2. Mast Cells
• Chemicals for example:
1. Tumor necrosis factor (TNF)
2. Interleukin-1 (IL-1)
3. Chemokines
4. Histamine
5. Kinin and bradykinin
6. Thrombin
• Leading to initiation of acute inflammatory response

13. Acute
Inflammation

14. Question
What is the major cell of acute inflammation in the first 24h?
What is the major cell of acute inflammation after the first 24h?

15. Acute Inflammation
Cells
Cells:
6-24h: Neutrophils
24-48h: Monocytes
Exception: Pseudomonas infection, viral infection,
allergic reaction

16. Acute Inflammation
Steps
1. Vascular reaction and changes.
2. Recruitment of Neutrophils to the site of inflammation.
3. Phagocytosis and clearance of offending agents

17. Question
What are the two common vascular changes that are seen in acute
inflammation?
What is the difference between exudate and transudate?

18. Acute Inflammation
(Step 1: Vascular Reaction)
• Vasodilation of arterioles by mediators such as
histamine:
1. Increased capillary bed and blood flow (Rubor and Color), brings more
neutrophils
2. Increases the hydrostatic pressure, helps filtration of fluid to extravascular
spaces.
3. Slower blood flow helps the margination and attachment of neutrophils to
endothelial cells (see the following)
• Increased Permeability (vascular leakage):
1. Immediate transient response (15-30 mins): contraction of endothelial cells
2. Endothelial Injury (several hours):injury by toxins, direct chemical or physical
injuries, is healed by thrombosis and repair.
3. Transcytosis: Transport of protein and fluids through endothelial cells,
activated by VEGF.
• Transudate VS. Exudate: Exudate means vascular
damage

19. Question
Can you recall three steps of leukocyte recruitment??

20. Acute Inflammation
Step 2: Leukocyte recruitment
• Margination: vasodilation results in slower blood flow,
therefore reduced wall shearing force and accumulation
of cells in periphery rather than central column of blood.
• Rolling: Leukocytes sequentially binds and detaches to
the receptors with low affinity on the surface of
endothelial cells. This results in rolling of leukocytes on
the surface of endothelial cells.
• Attachment: Leukocytes binds to the receptors with
high affinity on the surface of endothelial cells

21. Acute Inflammation
Step 2: Leukocyte recruitment
• Rolling: Is mediated by family of cell surface receptors
found on endothelial and leukocyte surface called
Selectin (CD62)
• Leukocytes: L-selectin
• Endothelial cells : E-selectin
• Platelets and Endothelial cells: P-selectin

22. Acute Inflammation
Leukocyte recruitment
1. Increase TNF, IL-1 and chemokine
o Endothelial cells: increase E-selectin and ligands for L-selectin.
o Neutrophils: increase L-selectin and ligands for E-selectin.
1. Increase histamin and thrombin
o Endothelial cells: redistribution of P-selectin from Wiebel Palade bodies.
o Neutrophils: Increase ligands for P-selectin.

23. Question
Can you recall the family of receptors for the attachment of
Leukocytes ??

24. Acute Inflammation
Leukocyte recruitment (Attachment)
Molecules Distribution Ligands
LFA-1
(CD11aCD18)
Neutrophils,
monocytes, T cells
(naïve, effector,
memory)
ICAM-1 (CD54), ICAM-2 (CD102);
expressed on endothelium
(upregulated on activated
endothelium)
MAC-1
(CD11bCD18)
Monocytes, DCs ICAM-1 (CD54), ICAM-2 (CD102);
expressed on endothelium
(upregulated on activated
endothelium)
VLA-4
(CD49aCD29)
Monocytes
T cells (naïve,
effector,
memory)
VCAM-1 (CD106); expressed on
endothelium (upregulated on activated
endothelium)
α4β7
(CD49DCD29)
Monocytes, T cells
(gut homing naïve
effector, memory)
VCAM-1 (CD106), MAdCAM-1;
expressed on endothelium in gut and
gut-associated lymphoid tissues

25. Acute Inflammation
Step 3: Phagocytosis and clearance of the offending agents
Recognition and attachment of the particle to be ingested
by leukocytes:
1. Mannose and Fucose terminal residue of glycoprotein
and glycolipids on microbial walls (human does not
contain these residues)
2. Scaveneger recptors on phagocytes: Integrin
CD11b/CD8
3. Engulfment with clathrin based coated pit
4. Formation of phagosome
5. Merging with lysosomes and formation of
phagolysosomes.

26. Question
Can you name three methods for destruction of offenders in
lysosomes?

27. Phagocytosis and clearance
of the offending agents
Intracellular destruction:
1. ROS: Respiratory burst, NADPH oxidase produce O2

Which later changes to H2O2 and reacts with CL- to form
OCl2
- (mediated by myeloperoxidase).
2. RNS: NO is formed by inducible NO synthase (iNOS)
and reacts with O2
- to form ONOO-.
3. Lysosomal Enzyme and Proteins:
o Specific Granules: Lysosyme, collagenase, lactoferin, plasminogen, alkaline
phosphatase.
o Azurophilic gransules: Myeloperoxidase, bactericidal factors (defensin), acid
hydrolase, neutral protease.

28. Question
Can you recall some of the antioxidant mechanisms?

29. Antioxidant and
antiproteases
Anti oxidants:
• Superoxide Dismutase
• Catalase
• Glutathione peroxidase
• Ceruloplasmine
• Iron free transferrin
Anti Proteases:
• α1- Antitrypsin
• α2-macroglubin

30. Question
Two Vasoactive amines and roles in inflammation??

31. Mediators of Infllamation
Vasoactive Amines
• Histamine:
1. Richest source: Mast cells but also in basophils and platelets
2. Released By: attachment of Ab to mast cells, anaphylatoxines (C3a and C5a)
and by direct injury (cold, warm), substance p and IL-1 and IL-8.
3. Function: vasodilation on arterioles through H1 receptors
• Serotonin:
1. Richest source: Platelets and NEC
2. Function: vasoconstrictor, function in inflammation unknown.

32. Question
Name two pathways for formation of Arachidonic Acid derivatives
that are involved in inflmmation?? Name the products.

33. AA derivative
(Eicosanoids)

34. Cyclooxygenase Pathway
and Prostaglandins (PG)
COX-1 and COX-2, COX-2 is activated specifically for inflammation.
• TXA2: Secreted by platelets, platelets aggregators and also a potent
vasoconstrictor.
• PGI2 (prostacyclin): Secreted by endothelial cells, potent inhibitor
of platelet aggregation, vasodilators.
• PGD2: Secreted by mast cells, chemoattractant for neutrophils,
vasodilator, increase permeability of post-capillary veins.
• PGE2: similar to PGD2 but secreted by almost any cell.
• PGF2α: smooth muscle contraction (uterine, bronchial walls, small
arterioles).
• PGE2: Hyperalgesia, is involved in cytokine induced fever.
Inhibitors: NSAID, Aspirin for both COX-1 and 2 and Coxib for COX-2

35. Lipooxygenase Pathway
and Leukotrienes (LT)
5-Lipooxygnease is one of the most important lipooxygenases.
• 5-hydroxyeicosatetranoic acid: an intermediate product, a potent
chmeoattractant for neutrophils
• LTB4: potent chmeoattractant for neutrophils
• LTC4, LTD4 and LTE4: Vasoconstriction, bronchospasm, increases
vascular permeability
• Lipoxin: inhibits recruitment of leukocytes therefore is an anti
inflammatory. Requires two steps for production; 1) intermediate
lipoxin released by neutrophils then converted to lipoxin by platelets.
Inhibitors:
1) lipooxygnease inhibitors: Zileuten,
2)leukotrienes receptor antagonists (Monteleukast).

36. Cytokines and Chemokines
TNF and IL-1
• Secreted by dendritic cells and macrophages
• Stimulated by immune complex, foreign bodies,
microbial products, physical injury.
• Role:
1. Formation of other cytokines, chemokines, growth
factors, eicosanoids.
2. Activation of leukocytes, production of NO.
3. Systemic acute phase reactant: Fever, SIRS, decrease
appetite, regulates energy balance. TNF causes
Cachexia

37. Chemokines
• Proteins 8-10 KDa, classified based on the position of
terminal Cysteines (C).
1. C-X-C: like IL-8 secreted by macrophages and
endothelial cells chmotactic agent for neutrophils.
2. C-C: Like Monocytes chemoattractant protein 1 (MCP-
1)
3. C: like Lymphotactin, chemoattractant for lymphocytes.
4. C-X3-C: Fractalkine, chemoattractant factor for
monocytes

38. Question
Name three pathways lead to activation of complement system.

39. Complement System
Three activation pathways

40. Complement System
• All three pathways lead to activation of an enzyme called C3
convertase which cleaves C3 to C3a and C3b.
• C3b accumulates and activates more formation of C3b, then
activates C5 convertase which cleaves C5 to C5a and C5b
• C5b activates late complement protein (C6-C9) to form
membrane attack complex (MAC).
• C5b and C3b are important for opsonization.
• Released C3a and C5a: activates anaphylaxis by release of
histamines, chemotactic agents, activation of AA pathways.
• MAC is important for lysis of microbes such as N.Gonnorhea,
deficiency causes predisposition

41. Complement System
Inhibitors and disease
• C1 inhibitor (C1-INH):inhibits C1 activity
Deficiency of C1-INH causes hereditary angioedema
• Decay Accelerating Factor (DAF): prevents formation
of C3 convertase
• CD59: Prevents formation of MAC
CD59 and DAF are attached to Glycophosphatidyl inositol
(GPI) anchor. Deficiency of formation of GPI, prevents the
action of CD59 and DAF on RBCs can causes paroxysmal
nocturnal hemoglobinuria (PNH)

42. Morphologic Pattern of
Acute Inflammation
• Serous inflammation: Low vascular permeability, Exudation
of cell-poor fluid. Examples Blister, Parapneumonic effusion.
• Fibrinous Inflammation: Higher vascular permeability,
Fibrinous exudate, mostly seen in the lining of body cavity,
such as pericardium or meninges, can dissolve completely or
changes to scar tissue (organization).
• Purulent inflammation (Abscess): necrotic tissue in the
middle, neutrophiles around the central core and fibroblasts,
vascular tissue at the outside of this lesion. Example:
appendicitis.
• Ulcer: a local defect, or excavation, of the surface of an organ
or tissue that is produced by the sloughing (shedding) of
inflamed necrotic tissue, Example: Gastric ulcer.

43. Outcomes of Acute
Inflammation
• Complete resolution with no or minimal scar tissue.
• Healing by connective tissue repair, scar formation and
fibrosis.
• Progression to chronic infection, due to persistence of
the injurious agent or difficulties in repair processing.

44. Chronic Inflammation

45. Chronic Inflammation
Causes
• Persistent infection:
o Infection is not cleared by innate inflammation,
o Examples: MTB, Some viral infection, parasites, fungal infection
• Hypersensitivity and autoimmune Diseases:
o Hypersensitivity type I-IV
o Autoimmune disease such as SLE, RA
• Prolong exposure to toxic agents:
o Talk, Slilcosis, Asbestosis

46. Question
Name two major type of cells involved in chronic inflammation.

47. Question
Where are the macrophages derived from?
Name three tissue macrophages.
Name Two methods of activation of macrophages.

48. Chronic Inflammation
Cells: Macrophages
• Macrophages:
o Derived from bone marrow, embryonic yolk sac and fetal liver.
o Circulate in blood as monocytes and transfer to tissue and resident macrophages
such as Kupfer cells, microglial cells, Langerhans cells, alveolar macrophages .
• Activation:
o Classical activation: by TLR or IFN-Υand foreign substance, Classically activated
macrophages (M1) are acting as the effector cells in inflammation.
o Alternative activation: By IL-4 and IL-13 of T-lymphocytes. These activated
macrophages (M2) are important in tissue repair by secreting growth factors that
promote angiogenesis, activate fibroblasts, and stimulate collagen synthesis.
• Function:
o Phagocytosis
o Tissue repair
o Secrete mediator of inflammation such as TNF and IL-1
o Antigen presenting cells

49. Question
Can you recall three major forms of CD4+ T cells and their function
in inflammation?

50. Chronic Inflammation
Cells: Lymphocytes
• Lymphocytes:
o Major cells of chronic inflammation and major cells of adaptive immunity.
o Antigen stimulated lymphocytes are recruited to the site of injury similar to
neutrophils.
• CD4+ T cells:
o TH-1 cells secrete IFN-Υand activates M1 macrophages .
o TH-2 cells secrete IL-4, IL-5 and IL-13 and activates M2 macrophages and also
eosinophils.
o TH-17 secrete IL-17 induces secretion of chemokines responsible for neutrophil
recruitment.
• Function:
o TH-1 and TH-17: against bacteria and viruses.
o TH-2: against helminthic parasites.
o Macrophages present the antigen to T cells and also secrete IL-12 to activate
these cells.

51. Chronic Inflammation
Cells: Others
• Eosinophils:
o Major basic protein extremely toxic for parasites.
• Mast Cells:
o Part of primary innate response by scereting inflammaotry mediators.
o Contains Fcε RI receptor for FC protion of IgE, therefore involves in allergic
reaction
• Neutrophils:
o Although involves in acute inflammation, they can be seen in burst of
inflammation as acute on chronic inflammation..

52. Systemic Effects of
Inflammation
• Acute phase response is mediated by TNF, IL-1 and IL-6.
1. Fever: Bacterial products such as LPS (exogenous pyrogens) stimulates leukocytes
to secrete TNF and IL-1 (endogenous pyrogens), induces COX which increases
PGE2, PGE2 at hypothalamic area increases neurotransmitters that set the
temperature at higher points.
2. Acute Phase Proteins: Examples are SAA, CRP and fibrinogen. They are produced
by liver and their levels increase 100 times following inflammation.
1. Fibrinogen binds to RBC causes rouleuax formation (bases of ESR)
2. Long time activation of SAA causes amyloidosis
3. Hepcidin another phase reactant protein reduce availability of iron and causes
anemia of chronic disease.
3. Leukocytosis
4. Other manifestations: such as rigors and chills, loss of appetite, malaise.
5. Septic shock: High levels of TNF and f IL-1 associated with DIC, hyperglycemia,
hypotension.

53. Question
Can you recall two types of reaction for tissue repair?
Hint: in regards to tissue that can proliferate vs. not.

54. Repair
• Two types of reaction:
1. Regeneration: by proliferation
of remained uninjured cells
and/or by activation of stem
cells.
2. Connective tissue
deposition and scar
formation: if injured tissue is
incapable of proliferation or
damage is so severe

55. Tissue Regeneration
Three types of cells:
1. Labile/Continuously dividing cells: such as majority of
surface epithelia, can regenerate as long as pool of stem
cells are preserved.
2. Stable quiescent (G0 phase) cells: such as solid organs,
fibroblast, endothelial and smooth muscle cells, only
regenerates in response to injury and have a limited
capability of regeneration.
3. Permanent tissue: Such as neuron, cardiac myocytes and
skeletal muscles, except to very limited stem cell
proliferation, they never regenerate

56. Tissue Regeneration
Liver
• Priming phase: priming
the hepatocyte by IL-6
secreted from Kupffer
cells.
• Growth factor phase:
From G0 to G1 and then S
phase on primed
hepatocytes by HGF and
TGF-α.
• Termination phase: return
to quiescence, by TGF-β.

57. Scar Formation
Steps of scar formation:
1. Angiogenesis
2. Deposition of connective tissue
These two first steps forms a tissue with a loose
extracellular matrix, proliferated fibroblasts and thin-walled
leaky vessels with presence of macrophages. This tissue is
called Granulation Tissue.
3. Remodeling of connective tissue

58. Scar Formation
Angiogenesis
1. Vascular Endothelial Growth
Factor (VEGF): specifically VEGF-
1 stimulates capillary sprouting
2. Fibroblast Growth Factor (FGF):
Specifically FGF-2 stimulates
endothelial proliferation.
3. Angiopoeitin 1 and 2: stabilized
newly formed vessels by the
recruitment of pericytes and
smooth muscle cells and by the
deposition of connective tissue.
4. PDGF and TGF-β: stabilizing the
tissue by enhanced production of
extracellular matrix

59. Deposition of Connective
Tissue
• M2 Macrophages release TGF-β, PDGF and FGF-2
which lead to migration and proliferation of fibroblast into
the site of injury.
• TGF-βstimulates synthesis and deposition of ECM
(collagen, fibronectin and elastin) by fibroblast and
inhibits matrix metalloproteinase (MMP), therefore
increases the net accumulation of collagen.
• Some of the fibroblasts also acquire features of smooth
muscle cells (myofibroblast) and are important in scar
contraction.

60. Remodeling of
connective tissue
• Removal and remodeling of extracellular matrix by Matrix
Metalloproteinase (MMP).
• MMP-1 to -3: are collagenase which cleaves fibrillar collagen.
• MMP-2 and -9 are gelatinase which cleaves fibronectin.
• MMP-3, -10 and -11 are stromelysins which cleaves ECM
constituents, including proteoglycans, laminin, fibronectin,
• tissue inhibitors of metalloproteinases (TIMPs), inhibits
MMP and contorls the remodeling.
• ADAMs (a disintegrin and metalloproteinase) family are
attached to plasma membrane and deactivates TNF, TGF-β,
and members of the EGF family.

61. Question
Give some examples for the factor that are able to affect tissue
repair?

62. Factor influencing repair
• Infection
• Diabetes
• Nutritional status: protein deficiency and Vit. C
deficiency.
• Steroids: preventing TGF-B production.
• Mechanical factors: pressure, torsion
• Poor perfusion
• Foreign body
• Type of tissue and extent of damage

63. Question
What is the difference between hypertrophic scar and keloids?

64. Abnormal Tissue Repair
• Fibrosis in internal organs activated by TGF-B.
• Inadequate formation of granulation tissue and scar:
leads to wound dehiscence and ulceration
• Excessive formation of the components of the repair
process can give rise to hypertrophic scars (raised
edge) and keloids (beyond the boundaries of original
wound.
• Exuberant granulation tissue, prevents reepithelialization
• contraction

65. Acute Inflammation
(Step 1: Vascular Reaction)
• Increased number of lymph vessels to remove the
exudates:
• Inflammation of Lymph Vessels: Lymphangitis
• Inflammation of draining lymph node: Reactive
Lymphadenitis