CHAPTER 2Inflammation

(5 OBJECTIVES)1) (Concept) Understand the chain,

progression, or sequence of vascular and cellular events in the histologic evolution of acute inflammation

2) (Rote?) Learn the roles of various “chemical mediators” of acute inflammation

3) Know the three possible outcomes of acute inflammation

4) Visualize the morphologic patterns of acute inflammation

5) Understand the causes, morphologic patterns, principle cells, minor cells, of chronic and granulomatous inflammation

SEQUENCE OF EVENTS• NORMAL HISTOLOGY • VASODILATATION • INCREASED VASCULAR PERMEABILITY • LEAKAGE OF EXUDATE • MARGINATION, ROLLING, ADHESION • TRANSMIGRATION (DIAPEDESIS) • CHEMOTAXIS • PMN ACTIVATION • PHAGOCYTOSIS: Recognition, Attachment,

Engulfment, Killing (degradation or digestion) • TERMINATION • 100% RESOLUTION, SCAR, or CHRONIC

INFLAMMATION are the three possible outcomes

ACUTE INFLAMMATION

•“PROTECTIVE” RESPONSE

•NON-specific

ACUTE INFLAMMATION• VASCULARVASCULAR EVENTS

• CELLULARCELLULAR EVENTS (PMN or PolyMorphonuclear Neutrophil, Leukocyte?, “POLY”, Neutrophil, Granulocyte, Neutrophilic Granulocyte

• ““MEDIATORS”MEDIATORS”

ACUTE INFLAMMATION

Neutrophil

Polymorphonuclear Leukocyte, PMN, PML

“Leukocyte”

Granulocyte, Neutrophilic granulocyte

“Poly-”

Polymorph

RuborRubor

CalorCalor

TumorTumor

DolorDolor

5th (functio laesa)

HISTORICAL

HIGHLIGHTS(Egypt, 3000 BC)

STIMULI for acute inflammation

• INFECTIOUSINFECTIOUS

• PHYSICALPHYSICAL

• CHEMICALCHEMICAL• Tissue Necrosis

• Foreign Bodies (FBs)

• Immune “responses”, or “complexes”

Vascular Changes• Changes in Vascular Flow

and Caliber

• Increased Vascular Permeability

INCREASED PERMEABILITY

• DILATATION

• Endothelial “gaps”

• Direct Injury

• Leukocyte Injury

• Transocytosis (endo/exo)

• New Vessels

LEAKAGE OF PROTEINACEOUS FLUID

(EXUDATEEXUDATE, NOT TRANSUDATE)

EXTRAVASATION of PMNs

• MARGINATION (PMN’s go toward wall)

• ROLLING (tumbling and HEAPING)

• ADHESION • TRANSMIGRATION

(DIAPEDESIS)

ADHESION MOLECULES(glycoproteins) affecting

ADHESION and TRANSMIGRATION

• SECRETINS (from endothelial cells)

• INTEGRINS (from many cells)

CHEMOTAXISPMNs going to the site of “injury”

AFTER transmigration

LEUKOCYTE“ACTIVATION”

• “triggered” by the offending stimuli for PMNs to:

– 1) Produce eicosanoids (arachidonic acid derivatives)• Prostaglandin (and thromboxanes)• Leukotrienes• Lipoxins

– 2) Undergo DEGRANULATION

– 3) Secrete CYTOKINES

PHAGOCYTOSIS• RECOGNITION

• ENGULFMENT

• KILLING (DEGRADATION/DIGESTION)

CHEMICAL MEDIATORS• From plasma or cellsFrom plasma or cells• Have “triggering” stimuliHave “triggering” stimuli• Usually have specific targetsUsually have specific targets• Can cause a “cascade”Can cause a “cascade”• Are short livedAre short lived

CLASSIC MEDIATORS• HISTAMINE

• SEROTONIN

• COMPLEMENT

• KININS

• CLOTTING FACTORS

• EICOSANOIDS

• NITRIC OXIDE

• PLATELET ACTIVATING FACTOR (PAF)

• CYTOKINES

• /CHEMOKINES

• LYSOSOME CONSTITUENTS

• FREE RADICALS

• NEUROPEPTIDES

HISTAMINE• Mast Cells,

basophils• POWERFUL

Vasodilator• Vasoactive

“amine”• IgE on mast

cell

SEROTONIN• (5HT, 5-Hydroxy-

Tryptamine)

• Platelets and EnteroChromaffin Cells

• Also vasodilatation, but more indirect

• Evokes N.O. synthetase (a ligase) from argenine

COMPLEMENT SYSTEM• >20

components, in circulating plasma

• Multiple sites of action, but LYSIS is the underlying theme

KININ SYSTEM• BRADYKININ is KEY component, 9 aa’s• ALSO from circulating plasma• ACTIONS

– Increased permeability– Smooth muscle contraction, NON vascular

–PAINPAIN

CLOTTING FACTORS

• Also from circulating plasma

• Coagulation, i.e., production of fibrin

• Fibrinolysis

EICOSANOIDS(ARACHIDONIC ACID DERIVATIVES)

• Part of cell membranes• 1) 1) ProstaglandinsProstaglandins (incl. Thromboxanes)

• 2) 2) LeukotrienesLeukotrienes• 3) 3) LipoxinsLipoxins (new)MULTIPLE ACTIONS AT MANY LEVELS

Prostaglandins(thromboxanes included)

• Pain

• Fever

• Clotting

Leukotrienes

• Chemotaxis

• Vasoconstriction

• Increased Permeability

Lipoxins

• INHIBIT chemotaxis

• Vasodilatation

• Counteract actions of leukotrienes

Platelet-Activating Factor(PAF)

• Phospholipid

• From MANY cells, like eicosanoids

• ACTIVATE PLATELETS, powerfully

CYTOKINES/CHEMOKINES• CYTOKINES are PROTEINS produced by

MANY cells, but usually LYMPHOCYTES and MACROPHAGES, numerous roles in acute and chronic inflammation

–TNFα, IL-1, by macrophages

• CHEMOKINES are small proteins which are attractants for PMNs (>40), e.g., CXC, CC, CX3C, XC families, PF-4, IL-8

NITRIC OXIDE• Potent vasodilator

• Produced from the action of nitric oxide synthetase from arginine

LYSOSOMAL CONSTITUENTS• PRIMARY• Also called

AZUROPHILIC, or NON-specific

• Myeloperoxidase• Lysozyme (Bact.)• Acid Hydrolases

• SECONDARY• Also called SPECIFIC

• Lactoferrin• Lysozyme• Alkaline Phosphatase• Collagenase

FREE RADICALS• O2 – (SUPEROXIDE)

•H2O2 (PEROXIDE)

•OH- (HYDROXYL RADICAL)

•VERY VERY

DESTRUCTIVE

NEUROPEPTIDES• Produced in CNS (neurons)

• SUBSTANCE P

• NEUROKININ A

OUTCOMES OFACUTE INFLAMMATION

• 1) 100% complete RESOLUTION

• 2) SCAR

• 3)CHRONIC inflammation

Morphologic PATTERNSof Acute INFLAMMATION

(EXUDATE)• SerousSerous (watery)

• FibrinousFibrinous (hemorrhagic, rich in FIBRIN)

• SuppurativeSuppurative (PUS)

• UlcerativeUlcerative

BLISTER, “Watery”, i.e., SEROUS

FIBRINOUS

PUS

=

PURULENT

ABSCESS

=

POCKET

OF

PUS

=

NEUTROPHILS

PURULENT, FIBRINOPURULENT

ULCERATIVE

SEQUENCE OF EVENTS• NORMAL HISTOLOGY • VASODILATATION • INCREASED VASCULAR PERMEABILITY • LEAKAGE OF EXUDATE • MARGINATION, ROLLING, ADHESION • TRANSMIGRATION (DIAPEDESIS) • CHEMOTAXIS • PMN ACTIVATION • PHAGOCYTOSIS: Recognition, Attachment,

Engulfment, Killing (degradation or digestion) • TERMINATION • 100% RESOLUTION, SCAR, or CHRONIC

inflammation

CHRONIC INFLAMMATION

(MONOS)

LYMPHOCYTE“MONO”CYTE

MACROPHAGE

HISTIOCYTE

APC

CAUSES ofCHRONIC INFLAMMATION• 1) PERSISTENCE of Infection

• 2) PROLONGED EXPOSURE to insult

• 3) AUTO-IMMUNITY

Cellular Players• LYMPHOCYTESLYMPHOCYTES• MACROPHAGESMACROPHAGES (aka, HISTIOCYTES)

• PLASMA CELLS• EOSINOPHILS• MAST CELLS

MORPHOLOGY• INFILTRATION

• TISSUE DESTRUCTION

• HEALING

GRANULOMASGRANULOMATOUS INFLAMMATION

4 COMPONENTS

FIBROBLASTS

LYMPHS

HISTIOSHISTIOS

“GIANT” CELLS

GRANULOMASGRANULOMATOUS INFLAMMATION

CASEATING (TB)

NON-CASEATING

LYMPHATICDRAINAGE

• SITE REGIONAL LYMPH NODES

SYSTEMIC MANIFESTATIONS(NON-SPECIFIC)

• FEVER, CHILLS

• C-Reactive Protein (CRP)

• “Acute Phase” Reactants, i.e., α1-α2

• Erythrocyte Sedimentation Rate (ESR) increases

• Leukocytosis

• Pulse, Blood Pressure

• Cytokine Effects, e.g., TNF(α), IL-1

NORMAL SPE

Serum

Protein

Electrophoresis

In ACUTE

Inflammation

Alpha-1 & alpha-2

are increased, i.e.,

“acute phase”

reactants.