Neutrophil

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Neutrophil InnateImmuneresponse
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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

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Neutrophil

• Neutrophil
• Granulocytes
• Polymorphonuclear (PMNs)
• Polymorphonuclear leukocytes (PMNLs)
• Polys

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Neutrophil
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Neutrophils innate immune response
Neutrophils eliminate bacterial infections
Figure 8.21
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Neutrophil-associated diseases

• Lung Adult Respiratory Distress Syndrome
• Asthma
• Asbestosis
• Emphysema
• Idiopathic pulmonary fibrosis

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Neutrophil-associated diseases
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Neutrophil-associated diseases

• Kidney Glomerulonephritis
• Interstitial nephritis
• Heart Myocardial reperfusion injury
• Ischemic heart disease
• Joint Rheumatoid arthritis
• Gout
• Systemic Scleroderma vasculitis

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Neutrophil

• The neutrophil is specialized for the
  phagocytosis and destruction of micro-organisms
  and damaged or necrotic tissues.

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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
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Neutrophil

• I. Morphology
• An abundance of granules
• Multi-lobed nucleus
• Prominent cytoskeleton for locomotion and
  chemotactic functions
• 1. microfilaments
• 2. microtubules
• 3. intermediate filaments

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Chemotaxis of the neutrophil
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Neutrophil

• II. Chemotaxis
• Endogenous factors
• C5a complement fragment
• IL-8
• Platelet Activating Factor (PAF)
• Leukotriene B4 (LTB4)
• Fragments of collagen and fibrin

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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.

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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.

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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

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Neutrophil chemotaxis

• Platelet Activating Factor (PAF)
• PAF is a small phospholipid (MW 300-500) which
  causes
• platelet aggregation
• increased vascular permeability
• chemotaxis

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Neutrophil chemotaxis

• II. Chemotaxis
• Exogenous factors bacterial products
• N-formylated oligopeptides (FMLP)
• Endotoxin (LPS)

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Neutrophil chemotaxis

• The bacterial cell wall component, LPS
  (endotoxin), is first bound by a serum protein,
  lipopolysaccharide-binding protein (LBP).
• The complex of LPS and LBP is then bound by CD14
  on the surface of the neutrophil.

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Neutrophil chemotaxis

• The interaction of CD14 with the LPS-LPB complex
  causes an increase in the adhesive activity of
  CR3 (CD11b/CD18) on neutrophils.

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Transvascular Migration of the Neutrophil
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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

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Margination Transmigration
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MARGINATION
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PHAGOCYTOSIS
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Enzymes of the Neutrophil
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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.

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Neutrophil enzymes
Primary Granules Myeloperoxidase Defensins Lyso
zyme Elastase Others BPI Cathepsin
G Alkaline phosphatase Proteinase
3 ?-glucuronidase ?-fucosidase Phospholipases
A2, C, D ?-mannosidase
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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).

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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.

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Neutrophil enzymes

• The activity of elastase is controlled by an
  inhibitor termed a1-anti-trypsin.
• Human neutrophil elastase (HNE) has been
  demonstrated in pathogenesis of emphysema, adult
  respiratory distress syndrome (ARDS), chronic
  bronchitis, rheumatoid arthritis, and psoriasis.

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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
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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.

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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.

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Neutrophil enzymes

• Collagenase acts as an anticoagulant because it
  digests fibrinogen.
• It is inhibited by a-1-antitrypsin and
  a-2-macroglobulin.
• Some diseases associated with over abundant
  collagenase secretion include rheumatoid
  arthritis and certain diseases of the eye like
  ulcerated corneas.

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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.
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Control of the Neutrophil Enzymes Anti-proteases
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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.

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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).

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a-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.

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a-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.

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a-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

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a-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.

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Emphysema

• PROTEIN-ENZYME IMBALANCE Neutrophil elastase is
  released during times of inflammation. This
  action is normally helpful and is balanced
  (neutralized) by the protein a-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 a-1 antitrypsin.

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Emphysema
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Emphysema
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Anti-proteases
Anti-protease shield prevents degradation of
normal tissues
Then how can the neutrophil perform its normal
functions?
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Deactivation of anti-proteases

• STEP ONE
• HOCl ?1-protease inhibitor (?1-PI),
  anti-leukoprotease (ALP),
  ?2-macroglobulin (?2-M), plasminogen
  activator inhibitor- 1 (PAI-1)
• STEP TWO
• Elastase metalloprotease (TIMP)
  a1-antichymotrypsin (a1-ACT)

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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.

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NEUTROPHIL
Monday will be Adhesion Proteins