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INFLAMMATION & REPAIR

Lecture 5 Acute Inflammation: Inflammatory Cell Types

Winter 2013

Chelsea Martin Special thanks to Drs. Hanna and Forzan

1. Vasodilation (increased blood flow) ► CALOR & RUBOR

• arteriolar dilation / opening of capillaries (hyperemia / redness)

• histamine and Nitric Oxide (primarily)

2. Increased microvascular permeability: fluids into tissues ► TUMOR

3. Blood flow slows (stasis) and rbc concentration ► RUBOR

4.Cellular events –

a) margination, rolling and adhesion

b) emigration of WBC into tissue (exudation)

c) accumulation of WBC at sites of injury

TUMOR

d) activation of cells, production of mediators

DOLOR

e) removal of stimulus

5. Tissue damage / Repair ►LOSS OF FUNCTION

SEQUENCE of EVENTS:

43

Leukocytes Cells of the Inflammatory Exudate

Polymorphonuclear Leukocytes • Neutrophils (heterophils)

• Eosinophils

• Basophils/Mast Cells

Mononuclear Cells • Monocytes/Macrophages

• Lymphocytes

• Plasma cells

• Thrombocytes*

Generalities 1. Most leukocytes are in the blood stream (WBCs)

• except: plasma cells, mast cells, macrophages

2. Leukocytes maintained in relative and constant proportion

• modified by systemic response to inflammation

3. Each blood cell plays a distinctive role

4. Each enters into inflammatory response in a definite sequence

Virchow vs. Cohnheim

The Theory of Inflammation

• Rudolph Virchow believed pus was made of connective tissue elements.

• Julius Cohnheim proved they came from the blood.

Erythrocyte

Platelet

Segmented neutrophil

Band neutrophil

Eosinophil

Basophil

Monocyte

Pathologystudent.com

Neutrophils

Synonyms:

• polymorphs, PMNs, Neuts

Characteristics

• highly mobile

• respond to lots of chemotaxins

• phagocytic and bactericidal

• 1º cell against bacteria

• 1st line of defense & crucial

• don’t divide in tissue

• short life-span - in circulation few days (hrs?)

- undergo apoptosis if not utilized

35

Neutrophils in suppurative

bronchitis (tissue - H&E)

Neutrophils

in cytologic preparation

Neutrophils - Where do they live?

• Originate in Bone Marrow

5-10 X 1010 per day

• Blood

Circulating Pool (measured in a CBC)

Marginating Pool (out of the flow)

• Storage pool in bone marrow

• Exit into tissue

die after 1-2 days

Neutrophil - Morphology

Abundant cytoplasmic granules:

• Azurophil Granules (1o granules)

• Myeloperoxidase & others

• Specific Granules (2o granules)

• Lysozyme & other enzymes

• Leukocyte adhesion molecules

• Tertiary granules

• Gelatinase

• Leukocyte adhesion molecules

Other enzymes - elastase, collagenase, plasminogen activators, etc

Neutrophil - Functions

• Phagocytosis ROS

H2O2 - myeloperoxidases - halide

lysosomal enzymes

• Mediate tissue injury

• Regulate inflammatory response release leukotrienes, PAF, etc

Myeloperoxidase (in azurophil granules)

catalyzes:

H2O2 + Cl- HOCl●

HOCl (Hypochlorous acid) is a powerful oxidant and antimicrobial agent

(H2O2-myeloperoxidase-halide system)

Myeloperoxidase

www.medirabbit.com

Heterophils Guinea pig

eosinophil vs heterophil

WHEN DO NEUTROPHILS PREDOMINATE?

• acute inflammatory reactions

• suppurative / purulent exudates

(esp bacterial infections)

Morph. Dx (pig):

Meningitis, suppurative, focally extensive, acute, severe

Morph. Dx (calf):

Hepatitis, suppurative, focal, acute, severe (abscess?)

Eosinophil - Morphology

• granules are basic

– eosin (acid) – red

• slightly larger than neutrophils,

variable size

• phagocytic (less than pmn’s)

26

Eosinophil - Morphology and Granules

Major basic protein

• parasite killing

• induce histamine release (mast cells)

Eosinophilic cationic protein

• parasite killing

• shortens coagulation time

Histaminase

• inactivates histamine

Pro

-in

fla

mm

ato

ry

Anti-I

nfla

mm

ato

ry

• Kill or damage helminths

• Involved in HS reactions

recruited by mast cell degranulation

(histamine & IL-5)

• Regulate inflammation

histaminase

Eosinophil - Functions

Eosinophil - Functions

• tumor-associated eosinophilia

– Mast cell tumors

– T cell lymphoma, etc.

• reduced numbers with corticosteroid therapy

Morph. Dx: Skin, mast cell tumor

with eosinophilic infiltration

http://cal.vet.upenn.edu

Plasmacytic inflammation Mast cell tumor

When do EOSINOPHILS predominate?

1. Parasitic diseases

Clinostomum marginatum

Heron trachea

2. Hypersensitivities and autoimmune conditions

Morph. Dx: Bronchitis, eosinophilic, subacute, severe

When do EOSINOPHILS predominate?

2. Hypersensitivities and autoimmune conditions

Morph. Dx: Myositis, eosinophilic, multifocal to coalescing, severe

Name of condition: Masticatory Myositis (MM)

Morph. Dx: Temporal & masseter muscles, atrophy, severe

When do EOSINOPHILS predominate?

Basophils and Mast Cells Characteristics

• Both have separate lineage in bone marrow

mast cells within tissue

basophils in circulation

• Receptors for IgE

main cell in HS type I (IgE mediated)

• Contain metachromatic granules

Histamine (+ proteases, etc)

• Don’t die after releasing granules

• Produce cytokines & AA metabolites

TNF, IL-3,-4,-5,-10,-13, Interferon

Leukotrienes, PG’s

18

Basophils and Mast Cells - Morphology

Mast cells

• round cells, abundant cytoplasm filled

with granules

• granules stain metachromatically with

toluidine blue or giemsa stains

• can proliferate in tissue

Basophils and Mast Cells - Morphology

Basophils

• nuclei are multilobed

• recruited at sites of HS’s

Neutrophil

Eosinophil

Basophil

Basophils Morphology - Species Differences

web.vet.cornell.edu/.../CPmodules/ heme1/images/basocomp.jpg

Basophils and Mast Cells - Functions

Acute Inflammation

• activated by IgE (parasities & allergies)

and substance P

• release histamine

• tryptase (tissue damage)

• generate cytokines

Recruitment of eosinophils

• IL-5

• LT-C4

Monocytes - Characteristics

Monocyte

• small reserve pool in bone marrow

• in circulation (t1/2 = 24-72 hrs)

• functional cells but require activation

• monocytes migrate into tissues macrophages monocyte

Macrophages - Characteristics

Macrophages (MØ’s)

• derived from circulating monocytes

(or resident MØ’s)

• t1/2 30-60 days in tissue

• motile - but sluggish

Macrophages/Monocytes - Morphology

• larger than neutrophils

• large nuclei (folded or bean-shaped)

• contain lysosomes

Macrophages - Functions

"Most dynamic and gifted of the leukocytes“

• Antimicrobial and phagocytic (O2 radicals)

• Recruit other leukocytes (chemokines/cytokines)

• Stimulate or modulate other cell activity

• Clean up debris

• Induce systemic effects

Source of: • Epithelioid macrophages

• Multinucleated giant cells

Leishmaniasis,Leishmania spp., canine

popliteal lymph node aspirate

Where do we see MACROPHAGES?

Acute Inflammation (in low numbers)

- with neutrophils

Subacute Inflammation

- with plasma cells/lymphocytes

Chronic Inflammation

- predominate in granulomatous inflammation

Repair

multinucleated giant cells

epithelioid macrophages

Lymphocytes and Plasma Cells - Characteristics

• less motile than PMN’s & macrophages

• recirculate (lymph nodes, lymphatics)

8

Lymphocytes and Plasma Cells

Morphology

• Heterogeneous

• T lymphocytes

– Cell mediated immunity

– Produce lymphokines

• B lymphocytes

– Produce plasma cells

– Important in antibody production

• review immunology notes

Lymphocytes and Plasma Cells

Morphology

• Heterogeneous

• T lymphocytes

– Cell mediated immunity

– Produce lymphokines

• B lymphocytes

– Produce plasma cells

– Important in antibody production

• review immunology notes

Where do we see LYMPHOCYTES & PLASMA CELLS?

1. Subacute Inflammation

2. Viral Infections

3. Immune-Mediated Diseases

4. Chronic Inflammation

Morph. Dx:

Encephalitis, lymphoplasmacytic,

multifocal, subacute, moderate

Name of Disease:

Distemper (Canine Morbillivirus)

Platelets - as inflammatory cells!

Contributions to inflammation

• Increase vascular permeability

Histamine

• Produce adhesion molecules

P selectin

• Release of inflammatory mediators activates complement (C5)

attracts neutrophils (chemotaxis)

Kierszenbaum, Histology and Cell Biology p 157, 2002

Cells of Inflammation

• Neutrophils

• Eosinophils

• Basophils/mast cells

• Monocytes/macrophages

• Lymphocytes/Plasma cells

• Platelets

• Endothelial cells

• Fibroblasts

Why are endothelial cells considered cells of the

inflammatory response?

Endothelial cells are the source of:

1. Pro-inflammatory mediators:

• Prostacyclin

• Prostaglandins

• PAF

• Interleukins (IL-1, IL-8)

• Nitric oxide

2. Adhesion molecules

• E-selectin

3. Anti-inflammatory mediators:

• TGF-β (anti-inflammatory, pro-repair)

Why are fibroblasts considered cells of the

inflammatory response?

Fibroblasts are the source of:

1. Pro-inflammatory mediators

• IL-6 B and T cell proliferation

2. Anti-inflammatory mediators

• TGF-β

Cells of Inflammation

• Neutrophils

• Eosinophils

• Basophils/mast cells

• Monocytes/macrophages

• Lymphocytes

• Platelets

• Endothelial cells

• Fibroblasts