INFLAMMATION IIINFLAMMATION II

Cellular EventsCellular Events

The cellular exudateThe cellular exudate

First exudation of fluid, later leukocytesFirst exudation of fluid, later leukocytes Exudation of leukocytesExudation of leukocytes

A. AdhesionA. Adhesion

B. EmigrationB. Emigration

C. ChemotaxisC. Chemotaxis Phagocytosis Phagocytosis

A. AdhesionA. Adhesion

Normal axial flow – leukocytes + RBCs, cell Normal axial flow – leukocytes + RBCs, cell free plasmafree plasma

Slowing or stasisSlowing or stasis→ widening of central → widening of central stream of cells, narrowing of plasma zone stream of cells, narrowing of plasma zone (loss by exudation)(loss by exudation)

White cells impinge upon the endothelium White cells impinge upon the endothelium which is sticky and line the endothelial which is sticky and line the endothelial surface (margination of surface (margination of WBCs/pavementation of the endothelium)WBCs/pavementation of the endothelium)

Adhesion( contd)Adhesion( contd)

Leukocyte adhesion molecules – glycoproteins Leukocyte adhesion molecules – glycoproteins LFA – 1,MO – 1,&p150,95 on the surface of cellsLFA – 1,MO – 1,&p150,95 on the surface of cells

Chemical mediator C5a & Leukotreine B4 (LTB4)Chemical mediator C5a & Leukotreine B4 (LTB4) Endothelial cell receptors stimulated by mediators Endothelial cell receptors stimulated by mediators

– endotoxin & interleukin 1 (IL-1), endothelial – endotoxin & interleukin 1 (IL-1), endothelial leukocyte adhesion molecule – 1 (ELAM-1)leukocyte adhesion molecule – 1 (ELAM-1)

Intracellular adhesion molecule (ICAM-1) serves Intracellular adhesion molecule (ICAM-1) serves as receptor for LFA-1 adhesion molecule on poly, as receptor for LFA-1 adhesion molecule on poly, mono, & lymphocytesmono, & lymphocytes

B. EmigrationB. Emigration

Adherent leukocytes > pseudopodiaAdherent leukocytes > pseudopodia ↓↓ between 2 endothelial cellsbetween 2 endothelial cells ↓ ↓Basement memb.& perivascular sheath (damaged by Basement memb.& perivascular sheath (damaged by

collagenases & proteases on surface of migrating collagenases & proteases on surface of migrating cells)cells)

First cells involved PMN – 1st 24 hrsFirst cells involved PMN – 1st 24 hrs→ → Monocytes/macrophages – next 24 hrs followed Monocytes/macrophages – next 24 hrs followed

by lymphocytes & RBCs – follow by diapedesis.by lymphocytes & RBCs – follow by diapedesis.

C. ChemotaxisC. Chemotaxis

The directional movement of an organism The directional movement of an organism in response to a chemical gradient is in response to a chemical gradient is chemotaxischemotaxis

Boyden`s chamber experimentBoyden`s chamber experiment

Chemotactic facors for leukocytesChemotactic facors for leukocytes

1.1. Leukotriene B4 (LTB4)Leukotriene B4 (LTB4)2.2. Platelet activating factor (PAF)Platelet activating factor (PAF)3.3. Components of complement system – C5aComponents of complement system – C5a4.4. Cytokines( IL8 )Cytokines( IL8 )5.5. Soluble bact. products (formylated peptides)Soluble bact. products (formylated peptides)6.6. Monocyte chemoattractant protein (MCP-1)Monocyte chemoattractant protein (MCP-1)7.7. Chemotactic factor for CD4 & TcellsChemotactic factor for CD4 & Tcells8.8. Eosinophil chemotactic factor of anaphylaxis Eosinophil chemotactic factor of anaphylaxis

(ECF – A)(ECF – A)

Chemotactic factorsChemotactic factors

Induce leukocyte activation alsoInduce leukocyte activation also ↓↓ - Production of arachidonic acid metabolites- Production of arachidonic acid metabolites -degranulation→ lysosomal enzymes-degranulation→ lysosomal enzymes -generation of O2 metabolites-generation of O2 metabolites - ↑ intracellular Ca - ↑ intracellular Ca -↑ in leukocyte surface adhesion molecules-↑ in leukocyte surface adhesion molecules

PhagocytosisPhagocytosis

Process of engulfment of solid particulate Process of engulfment of solid particulate material by the cells.material by the cells.

Cells ( phagocytes) –Cells ( phagocytes) –

1.PMNs (early ac. Inflammation)1.PMNs (early ac. Inflammation)

2.Circulating monocytes and fixed tissue 2.Circulating monocytes and fixed tissue mononuclear phagocytes - macrophages mononuclear phagocytes - macrophages

Phagocytosis (contd.)Phagocytosis (contd.)

Energy for phagocytosis from anaerobic Energy for phagocytosis from anaerobic glycolysisglycolysis

Phagocytosis Phagocytosis →→ series of metabolic events series of metabolic events (Respiratory burst)(Respiratory burst)

- - ↑utilisation of glucose through hexose ↑utilisation of glucose through hexose monophosphate shunt → result release of monophosphate shunt → result release of powerful oxidising agents – superoxide radical powerful oxidising agents – superoxide radical O2&H2O2 → intracellular destruction of bacteriaO2&H2O2 → intracellular destruction of bacteria

Surface phagocytosis – fibrin network >trapping Surface phagocytosis – fibrin network >trapping of org. by PNMs without prior opsonisationof org. by PNMs without prior opsonisation

PhagocytosisPhagocytosis

4 steps4 steps

1.1. Attachment stage ( opsonisation)Attachment stage ( opsonisation)

2.2. Engulfment stageEngulfment stage

3.3. Secretion ( degranulation stage)Secretion ( degranulation stage)

4.4. Killing or degradation stageKilling or degradation stage

Attachment stageAttachment stage

Phagocytes & micro- org > -vely charged Phagocytes & micro- org > -vely charged particles > repel each otherparticles > repel each other

Opsonins (naturally occuring substances in Opsonins (naturally occuring substances in serum)serum)

- IgG opsonin + receptor on the surface of - IgG opsonin + receptor on the surface of phagocyte (Fc fragment) phagocyte (Fc fragment)

- C3b opsonin- C3b opsonin++ corresponding receptor on corresponding receptor on the phagocyte the phagocyte

Engulfment stageEngulfment stage

Pseudopods around the particle Pseudopods around the particle →Phagocytic vacuole→breaks from cell →Phagocytic vacuole→breaks from cell surface& lies free in cell cytoplasm.surface& lies free in cell cytoplasm.

PV+lysosomes fuse →Phagolysosome/PV+lysosomes fuse →Phagolysosome/

Phagosome.Phagosome.

SECRETION(DEGRANULATION SECRETION(DEGRANULATION STAGE STAGE))

Preformed granulePreformed granule→discharged into →discharged into phagosomephagosome

Specific granules fuse first- liberateSpecific granules fuse first- liberate

Lysozyme,lactoferrin&alk.PO4ase.Lysozyme,lactoferrin&alk.PO4ase. Later azurophilic granules fuse→release Later azurophilic granules fuse→release

lysosomal enzymes &PNM →degranulatedlysosomal enzymes &PNM →degranulated

SECRETION.contdSECRETION.contd

Mononuclears synthesise & secrete Mononuclears synthesise & secrete enzymes( interleukins 2&6,TNF→(act as enzymes( interleukins 2&6,TNF→(act as pyrogens→fever))pyrogens→fever))

-arachidonic acid metabolites -arachidonic acid metabolites (prostaglandins,leukotrienes, PAF)&(prostaglandins,leukotrienes, PAF)&

O2metabolites(superoxideO2,H2O2,O2metabolites(superoxideO2,H2O2,

hypochlorous acid.)hypochlorous acid.)

KILLING or DEGRADATION KILLING or DEGRADATION STAGESTAGE

MICRO-ORGANISMS KILLED BY ANTIBACTERIAL MICRO-ORGANISMS KILLED BY ANTIBACTERIAL SUBS ARE DEGRADED BY HYDROLYTIC ENZYMESSUBS ARE DEGRADED BY HYDROLYTIC ENZYMES

ANTIBACTERIAL AGENTS ACT BY-ANTIBACTERIAL AGENTS ACT BY-

1. O2 dependent bactericidal mech.(by prodn. Of 1. O2 dependent bactericidal mech.(by prodn. Of reactive O2 metabolitesreactive O2 metabolites→(eliminate micro-org. growing →(eliminate micro-org. growing within phagocyteswithin phagocytes))))

2.O2 independent bactericidal mech.-2.O2 independent bactericidal mech.-

(lysosomal hydrolases, permeability increasing (lysosomal hydrolases, permeability increasing factors,defensins,cationic proteins)factors,defensins,cationic proteins)

3.Nitric acid mech. In exptal animals- fungicidal & 3.Nitric acid mech. In exptal animals- fungicidal & antiparasitic action.antiparasitic action.

Activities of PMN in Ac. Infln.Activities of PMN in Ac. Infln.

RANDOM MOVT.RANDOM MOVT. CHEMOTAXISCHEMOTAXIS ADHERENCE TO BACTERIA & PARTICLESADHERENCE TO BACTERIA & PARTICLES PHAGOCYTOSISPHAGOCYTOSIS ACTIVATION OF HEXOSE ACTIVATION OF HEXOSE

MONOPHOSPHATE SHUNTMONOPHOSPHATE SHUNT BACTERICIDAL ACTIVITYBACTERICIDAL ACTIVITY

DEFECT IN ANY OF THESE DEFECT IN ANY OF THESE MECH.MECH.→↓RESISTANCE TO INFN.→↓RESISTANCE TO INFN.

Local sequelae of ac. Infln.Local sequelae of ac. Infln.

Changes following ac. Infln. Depends on :Changes following ac. Infln. Depends on : 1. the amount of tissue damage 1. the amount of tissue damage 2. whether or not the causative agent remains.2. whether or not the causative agent remains. Some agentsSome agents→ destruction of fixed tissues. If pt. → destruction of fixed tissues. If pt.

survives,1.autolysis of the area> macrophages survives,1.autolysis of the area> macrophages infiltrate→ healing by repair & regeneration infiltrate→ healing by repair & regeneration 2.digestion of the area by lysosomal enzymes of 2.digestion of the area by lysosomal enzymes of PMN (pus cells) → abscess.PMN (pus cells) → abscess.

If no tissue death,- PMN → mononuclears → If no tissue death,- PMN → mononuclears → onset of demolition phase onset of demolition phase

Demolition phaseDemolition phase

MacrophagesMacrophages (scavengers) engulf-fibrin,red (scavengers) engulf-fibrin,red cells ,pus cells, foreign materials, bacteria.cells ,pus cells, foreign materials, bacteria.

- fuse to produce giant cells- fuse to produce giant cells

- act best when activated ( MAF identical to - act best when activated ( MAF identical to InterferonInterferon gamma)↓ gamma)↓

bacterial endotoxinsbacterial endotoxins

phagocytose bacteriaphagocytose bacteria

Functions of macrophagesFunctions of macrophages

Antimicrobial defenceAntimicrobial defence Immunological functionsImmunological functions Cellular immunityCellular immunity Antitumor activityAntitumor activity Control of granulopoiesisControl of granulopoiesis Control of erythropoiesisControl of erythropoiesis Secrtory activitySecrtory activity→lysosomal enzymes, →lysosomal enzymes,

lysozyme,plasminogen activators & lysozyme,plasminogen activators & inhibitors,collagenases, elastase, complement inhibitors,collagenases, elastase, complement components,prostaglandins,leukotrienscomponents,prostaglandins,leukotriens

End resultsEnd results

1.1. Resolution – complete return to normalResolution – complete return to normal

Demolition phase Demolition phase → removal of exudate – → removal of exudate – resolutionresolution

Removal of exudate delayed – fibrin Removal of exudate delayed – fibrin invaded by granulation tissue invaded by granulation tissue (organisation) – heals by fibrosis(organisation) – heals by fibrosis

End results(Contd.)End results(Contd.)

2. Suppuration2. Suppuration Infl. reaction associated with necrosisInfl. reaction associated with necrosis→→ suppuration suppuration Necrotic material > softening > fluid pus in a cavity > abscessNecrotic material > softening > fluid pus in a cavity > abscess Pus – dead & dying leukocytesPus – dead & dying leukocytes -- other components of infl. (oedema fluid,fibrin)-- other components of infl. (oedema fluid,fibrin) --organisms (many living – culture)--organisms (many living – culture) -- tissue debris (nucleic acids & lipids)-- tissue debris (nucleic acids & lipids) Epithelial surface involved > ulcer-- floorEpithelial surface involved > ulcer-- floor→necrotic tissue,ac. Infl. →necrotic tissue,ac. Infl.

exudate(slough)↓exudate(slough)↓ gets detached– heals by repair &regeneration.gets detached– heals by repair &regeneration. Abscess > drained /not drainedAbscess > drained /not drained↓↓ dense fibrous tissue,watery content dense fibrous tissue,watery content

absorbed,calcification. absorbed,calcification.