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Inflammation-3
INTRODUCTION:
“Inflame” – to set fire.
Inflammation is the “Dynamic response of
vascularised tissue to injury.”
Host response to get rid of damaged or necrotic
tissues and foreign invaders.
Is a protective response.
Serves to bring defense and healing
mechanisms to the site of injury.
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Inflammation-4
ACUTE INFLAMMATION
It is a complex reaction to injurious agents such as
microbes and damaged, usually necrotic cells, that
consists of vascular responses, migration and activation
of leukocytes and systemic reactions.
The unique feature of the inflammatory process is the
reaction of blood vessels, leading to the
accumulation of fluid and leukocytes in extravascular
tissues.
It is divided into 2 patterns-
1) Acute
2) Chronic
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Inflammation-5
ACUTE INFLAMMATION
Rapid in onset (seconds or minutes)
Is of relatively short duration, lasting for minutes, several
hours or a few days
It has 3 major components-
alterations in vascular caliber that lead to an increase in
blood flow
structural changes in the microvasculature that permit
plasma proteins and leukocytes to leave the circulation
emigration of the leukocytes from the microcirculation,
their accumulation in the focus of injury, and their
activation to eliminate the offending agent
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HAEMODYNAMIC CHANGES
Transient vasoconstriction
Persistent progressive vasodilatation
Elevation in local hydrostatic pressure resulting in
transudation of fluid into the extracellular space
Slowing or stasis
Leukocytic margination
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Vasodilation
Brief arteriolar vasoconstriction followed by
vasodilation
Accounts for warmth and redness
Opens microvascular beds
Increased intravascular pressure causes an
early transudate (protein-poor filtrate of plasma)
into interstitium.
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Chemotaxis
The chemotactic factor mediated transmigration of
leukocytes after crossing several barriers to reach the
interstitial tissues is called chemotaxis
The agents acting as potent chemotactic substances for
different leukocytes called chemokines are:
-Leukotriene B4 (LTB4)
-Platelet factor 4 (PF4)
-Components of complement system (C3, C5)
-Cytokines (IL-1,IL-5,IL-6)
-Soluble bacterial products (formylated peptides)
-Monocyte chemo-attractant protein (MCP-1)
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Inflammation-36
PHAGOCYTOSIS
It is the process of engulfment of solid
particulate material by the cells
There are 2 types of phagocytic cells-
-polymorphonuclear neutrophils called as
microphages
-circulating monocytes and fixed tissue
mononuclear phagocytes called as macrophages
It involves the following steps-
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Inflammation-40
OPSONIZATION
MAKING IT TASTY AND ATTRACTIVE
• PARTICLE– microbes
or bacterial products
or toxins
Opsonins: IgG antibody, protein
C3, mannose binding lectin,
fibronectin,fibrinogen and C-
reactive protein
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Inflammation-42
Killing and Degradation
Oxygen Dependent Systems: formation of
reactive oxygen species
NADPH oxidase enzyme complex
Hydrogen Peroxide—MPO—Halide system
Most potent bactericidal system of neutrophils
Polymorphs after phagocytosis undergo
apoptotic cell death
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Kinin system
Leads to formation of bradykinin from
cleavage of precursor (HMWK)
Vascular permeability
Arteriolar dilatation
Non-vascular smooth muscle contraction (e.g.,
bronchial smooth muscle)
Causes pain
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Complement system
Components C1-C9 present in inactive form
Activated via classic (C1) or alternative (C3)
pathways to generate MAC (C5 – C9) that
punch holes in microbe membranes
In acute inflammation
Vasodilatation, vascular permeability, mast
cell degranulation: C3a, C5a
Leukocyte chemotaxis :C5a
As an opsonin, increases phagocytosis: C3b
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Inflammation-54
Specific Mediators
PAF (platelet activating factor:
Derived also from cell membrane phospholipid
causes vasodilatation,
increased vascular permeability,
increases leukocyte adhesion
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Inflammation-55 Specific mediators
Cytokines
Polypeptide products of many cell types but mainly
lymphocytes and macrophages that act on same cell
autocrine, as a message to other cells paracrine
effect or systemically endocrine effect .
Increase endothelial cell adhesion molecule
expression and activation and aggregation of PMNs.
IL-1, TNF-α and -β, IFN-γ are especially important
in inflammation.
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Specific mediators
Nitric Oxide
short-acting soluble free-radical gas.
Produced by endothelial cells, macrophages,
causes:
Vascular smooth muscle relaxation and
vasodilatation
Kills microbes in activated macrophages
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Inflammation-57
Specific mediators
Lysosomal components
Leak from PMNs and macrophages after
demise, attempts at phagocytosis.
Acid proteases (only active within lysosomes).
Neutral proteases such as elastase and
collagenase are destructive in ECM.
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Inflammation-59FACTORS DETERMINING VARIATION IN
INFLAMMATORY RESPONSE
1) Factors involving the organisms
-type of injury
-virulence
-dose
2) Factors involving the host
-general health of host
-immune state of host
-leukopenia
-local host factors
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MORPHOLOGY OF ACUTE INFLAMMATION
PSEUDOMEMBRANOUS INFLAMMATION
-it is inflammatory response of mucous surface (oral,
bowel, respiratory) to toxins of diphtheria or irritant
gases.
ULCER
-it is local defect on the surface of an organ produced by
inflammation
-common sites are stomach, duodenum, typhoid,
intestinal tuberculosis, bacillary and amoebic dysentery
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SUPPURATION (ABSCESS FORMATION)
- contains purulent exudate or pus and the process
of abscess formation is known as suppuration -boil,
carbuncle
CELLULITIS
-it is a diffuse inflammation of soft tissues resulting
from spreading effects of substances like
hyaluronidase released by some bacteria