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Neutrophil
– Innate
Immune
response
Neutrophil
• Know mediators that prime and stimulate
the neutrophil function
• Know mediators secreted by the
neutrophil
• Understand the role of anti-proteinases in
neutrophil function
• Know immunomodulators of neutrophils
function
Neutrophil
•
•
•
•
Neutrophil
Granulocytes
Polymorphonuclear (PMNs)
Polymorphonuclear
leukocytes (PMNLs)
• Poly’s
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Neutrophil
Neutrophils –
innate immune response
Neutrophils
eliminate
bacterial
infections
Figure 8.21
Neutrophil-associated diseases
• Lung
Adult Respiratory Distress Syndrome
Asthma
Asbestosis
Emphysema
Idiopathic pulmonary fibrosis
Neutrophil-associated
diseases
Neutrophil-associated diseases
• Kidney
• Heart
• Joint
• Systemic
Glomerulonephritis
Interstitial nephritis
Myocardial reperfusion injury
Ischemic heart disease
Rheumatoid arthritis
Gout
Scleroderma vasculitis
Neutrophil
• The neutrophil is specialized
for the phagocytosis and
destruction of microorganisms and damaged or
necrotic tissues.
Neutrophils in the body
• 3-6,000/mL of blood
• ~70% of WBC
• T1/2 = 6-7 hours in blood
• T1/2 = 1-2 days in tissues
KNOW
Neutrophil
I. Morphology
A. An abundance of granules
B. Multi-lobed nucleus
C. Prominent cytoskeleton for locomotion
and chemotactic functions
1. microfilaments
2. microtubules
3. intermediate filaments
Chemotaxis
of the neutrophil
Neutrophil
II. Chemotaxis
A. Endogenous factors
1.
2.
3.
4.
5.
C5a – complement fragment
IL-8
Platelet Activating Factor (PAF)
Leukotriene B4 (LTB4)
Fragments of collagen and fibrin
Neutrophil chemotaxis
• C5a (C3a, C4a) act on specific receptors
to produce similar local inflammatory
responses (anaphylatoxins).
• C5a is the most stable, has the highest
specific biological activity, and acts on the
best defined receptor.
• All three induce smooth muscle contraction
and increase vascular permeability.
Neutrophil Chemotaxis
• C5a also acts directly on neutrophils
to increase their adherence to vessel
walls, their migration toward sites
of antigen deposition, and their
ability to ingest particles.
Neutrophil chemotaxis
• IL-8
• Chemokine produced by endothelial
cells, macrophages, bronchial epithelial
cells, fibroblasts, and keratinocytes.
• IL-8 is a very strong chemoattractant for
neutrophils and T-lymphocytes
Neutrophil chemotaxis
• Platelet Activating Factor (PAF)
• PAF is a small phospholipid (MW
300-500) which causes:
• platelet aggregation
• increased vascular permeability
• chemotaxis
Neutrophil chemotaxis
II. Chemotaxis
B. Exogenous factors – bacterial
products
1. N-formylated oligopeptides (FMLP)
2. Endotoxin (LPS)
Neutrophil chemotaxis
• The bacterial cell wall component,
LPS (endotoxin), is first bound by a
serum protein, lipopolysaccharidebinding protein (LBP).
• The complex of LPS and LBP is then
bound by CD14 on the surface of the
neutrophil.
Neutrophil chemotaxis
• The interaction of CD14 with the
LPS-LPB complex causes an increase
in the adhesive activity of CR3
(CD11b/CD18) on neutrophils.
Transvascular Migration
of the Neutrophil
Neutrophil activation
1) Surface changes from smooth to
ruffled membrane
2) Adhesion to endothelial cells
3) On surface: opsonins binding to C3b
or Fc portion of Ig
4) Membrane invaginates and forms
phagosome
5) Release of enzymes which mediate
destruction of target material
Margination
: Transmigration
MARGINATION
PHAGOCYTOSIS
Enzymes of the Neutrophil
Neutrophil enzymes
• Azurophilic or Primary (blue)
• These are the first granules formed in the
developing neutrophil and peak degranulation
is 90 minutes.
• Specific or Secondary (pink)
• These granules are formed later in the
development of the neutrophil. These
enzymes are released within 15 seconds after
contact with the pathogen.
Neutrophil enzymes
Primary Granules
Myeloperoxidase
Defensins
Lysozyme
Elastase
Others
BPI
Cathepsin G
Alkaline phosphatase
Proteinase 3
-glucuronidase
-fucosidase
Phospholipases A2, C, D
-mannosidase
Neutrophil enzymes
• Myeloperoxidase (MPO): is an
abundant granular enzyme (accounts for
5% of dry weight of the neutrophil).
• This enzyme combines hydrogen peroxide
with chloride ions to form hypochlorous
acid (HOCl = bleach).
Neutrophil enzymes
• Elastase: is a serine protease which
specifically hydrolyzes elastin.
• Elastin is the major component of elastic
fibers which stretch in the walls of blood
vessels, lungs, and ligaments.
Neutrophil enzymes
• The activity of elastase is controlled by
an inhibitor termed 1-anti-trypsin.
• Human neutrophil elastase (HNE) has
been demonstrated in pathogenesis of
emphysema, adult respiratory distress
syndrome (ARDS), chronic bronchitis,
rheumatoid arthritis, and psoriasis.
Neutrophil enzymes
Secondary granules
Lactoferrin
Lysozyme
Collagenase
Others
Gelatinase
Vitamin B12-binding protein
Cytochrome b558
fMLP receptor
CD11b/CD18, CD11c/CD18 (integrins)
Complement receptor 3 (CR3)
Histaminase
Plasminogen activator
Neutrophil enzymes
• Lysozyme: like MPO, is a microbicidal
enzyme.
• Lysozyme digests debris from cell walls
of bacteria that have already been
processed by other enzymes.
• Another function of lysozyme is to
modulate inflammation by suppressing
neutrophil chemotaxis and oxidative
metabolism.
Neutrophil enzymes
• Collagenase: cleaves collagen into two
distinct and specific peptide fragments
• Collagenase is released by intact
neutrophils during phagocytosis as a
collagenase precursor (procollagenase)
and is activated by trypsin, hypochlorous
acid or rheumatoid synovial fluid.
Neutrophil enzymes
• Collagenase acts as an anticoagulant
because it digests fibrinogen.
• It is inhibited by -1-antitrypsin and
-2-macroglobulin.
• Some diseases associated with over
abundant collagenase secretion include
rheumatoid arthritis and certain diseases
of the eye like ulcerated corneas.
Within 30 seconds after a
neutrophil ingests a
particle, it begins to
secrete specific granule
components into the
phagosome via
phagolysosomal fusion.
Within 3 minutes,
azurophil granule
components are
discharged into the
phagolysosome.
Control of the
Neutrophil Enzymes
Anti-proteases
Anti-proteinases
• There are normal regulatory mechanisms
for control of secreted neutrophil enzymes
and control pathways to limit the enzyme
action by anti-proteases.
• These are highly important for
neutralization of the enzymatic activities
of the neutrophil proteases.
Anti-proteinases
• Protease inhibitors can comprise about
10% of the total protein of the blood.
• Anti-protease activities are closely coupled
to the generation of neutrophil reactive
chlorinated oxidants (HOCl).
-1 Antitrypsin Deficiency (AATD)
• What is it?
• Alpha-1 antitrypsin is a protease inhibitor
(PI), genotype MM, which protects tissues
from the effects of neutrophil.
• It is mainly produced in the liver.
-1 Antitrypsin Deficiency (AATD)
• Who does it affect?
• Alpha-1 antitrypsin deficiency is genetic
and it is passed onto children by their
parents.
• There are at least 75 different variations,
or alleles, of the gene. Each person has
two alleles and can pass one of these on
to their children.
-1 Antitrypsin Deficiency (AATD)
• Most people carry two copies of the M
allele ie genotype MM. People with AATD
carry two copies of the Z allele ie
genotype ZZ.
• About 1 : 25 are MZ. They are usually
completely healthy but their partner will
also have a 1 : 25 risk of being MZ. If
they have children, each child will have a
1 : 4 chance of being ZZ, so the overall
risk for a child being ZZ is 1 : (25 x 25 x
4) = 1 : 2,500
-1 Antitrypsin Deficiency (AATD)
• Alpha-1 antitrypsin deficiency is the most
common genetic cause of liver disease
children and of emphysema in adults.
• It is also the most common genetic
disease for which liver transplantation is
undertaken in children.
Emphysema
• PROTEIN-ENZYME IMBALANCE
Neutrophil elastase is released during times of
inflammation. This action is normally helpful and
is balanced (neutralized) by the protein -1
antitrypsin produced in the liver.
• One cause of damage to the alveoli of the lung
is that elastase is produced by neutrophil but
there is a genetically lack of -1 antitrypsin.
Emphysema
Emphysema
Anti-proteases
Anti-protease
shield
prevents degradation
of normal tissues
Then how can the neutrophil
perform its normal functions?
Deactivation of anti-proteases
STEP ONE
• HOCl
1-protease inhibitor (1-PI),
anti-leukoprotease (ALP),
2-macroglobulin (2-M),
plasminogen activator inhibitor1 (PAI-1)
STEP TWO
• Elastase
metalloprotease (TIMP)
1-antichymotrypsin
(1-ACT)
Anti-proteases
• Subsequent to this
two staged attack on
anti-proteases, the
neutrophil enzymes
are free to damage
the bacterial targets,
necrotic tissues, or in
pathological
conditions, normal
tissues.
NEUTROPHIL
Monday will be Adhesion Proteins