PALOMAR COLLEGE Biology 201 Fundamentals of Biology II Rob Mustard Adjunct Faculty

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Biology 201Biology 201Fundamentals of Biology IIFundamentals of Biology II

Rob MustardRob Mustard

Adjunct FacultyAdjunct Faculty

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Leukocytes & Immune ResponseLeukocytes & Immune Response

Blood cells are one of the “fluid” Connective Blood cells are one of the “fluid” Connective TissuesTissues

Red blood cells Red blood cells (erythrocytes)(erythrocytes) Mammalian RBCs lack Mammalian RBCs lack

nuclei and mitochondrianuclei and mitochondria ~7 ~7 m diameterm diameter

White blood cellsWhite blood cells(leukocytes)(leukocytes) Giemsa stain to Giemsa stain to

differentiate WBCsdifferentiate WBCs6-7 million erythrocytes / ml6-7 million erythrocytes / ml33

7,000 leukocytes / ml7,000 leukocytes / ml33


Immune Response ModesImmune Response Modes

Innate ImmunityInnate Immunity Rapid (and general) response to a broad Rapid (and general) response to a broad

range of microbial invasionrange of microbial invasion Acquired (Adaptive) ImmunityAcquired (Adaptive) Immunity

Secondary (and highly-specific) response to Secondary (and highly-specific) response to previously-encountered pathogenspreviously-encountered pathogens

Vertebrates have Vertebrates have bothboth forms of immune- forms of immune-response mechanismsresponse mechanisms


Innate ImmunityInnate Immunity External defenses include:External defenses include:

Skin:Skin: impenetrable to most viruses & bacteria impenetrable to most viruses & bacteria Mucous:Mucous: viscous fluid that traps microbes viscous fluid that traps microbes Cellular secretions:Cellular secretions: sebaceous (oil) & sweat sebaceous (oil) & sweat

glands reduce skin’s pH to 3-5; lysozyme glands reduce skin’s pH to 3-5; lysozyme digests Gram + cell wallsdigests Gram + cell walls

Internal defenses begin after bacteria Internal defenses begin after bacteria invade, typically through a break in skin or invade, typically through a break in skin or other epidermal layerother epidermal layer


Inflammatory ResponseInflammatory Response Tissue damage from physical injury leads to Tissue damage from physical injury leads to

cascade of chemical signalscascade of chemical signals Histamine, stored in mast cells in connective Histamine, stored in mast cells in connective

tissuetissue Nearby capillaries become dilated and leaky, Nearby capillaries become dilated and leaky,

allowing passage of macrophages and increased allowing passage of macrophages and increased blood flowblood flow

Increased local blood supply leads to redness, Increased local blood supply leads to redness, heat and swelling (inflammation)heat and swelling (inflammation)

Macrophages move out into damaged tissues, in Macrophages move out into damaged tissues, in interstitial spaces between cellsinterstitial spaces between cells

Nonspecific Inflammatory Response


Leukocytes Involved in Leukocytes Involved in Innate Immunity: Innate Immunity: PhagocytesPhagocytes

NeutrophilsNeutrophils 60-70% of all leukocytes, 60-70% of all leukocytes,

live only a few dayslive only a few days Big: 12-15 Big: 12-15 m (2x m (2x

erythrocytes)erythrocytes) Nucleus has 2-5 lobes Nucleus has 2-5 lobes

(polymorphic)(polymorphic) MonocytesMonocytes

5% of all leukocytes5% of all leukocytes Biggest:Biggest: 20 20 mm Lighter, “frothy” horseshoe-Lighter, “frothy” horseshoe-

shaped nucleusshaped nucleus

Neutrophils are Neutrophils are granulargranular

Monocytes are Monocytes are agranularagranular


Leukocytes Involved in Leukocytes Involved in Innate Immunity: Innate Immunity: PhagocytesPhagocytes

EosinophilsEosinophils RareRare in blood smears (2-4%) in blood smears (2-4%) Big: 12-15 Big: 12-15 m (same size as m (same size as

Neutrophils)Neutrophils) Nucleus has 2 lobesNucleus has 2 lobes

Dendritic CellsDendritic Cells Patrol interstitial spaces of Patrol interstitial spaces of

skin & mucosal membranesskin & mucosal membranes Phagocytize invaders, Phagocytize invaders,

process & present antigen process & present antigen material (APCs)material (APCs)

Activate acquired immune Activate acquired immune systemsystem

Eosinophils are Eosinophils are granulargranular


Leukocytes Involved in Innate Leukocytes Involved in Innate Immunity: Immunity: HypersensitivityHypersensitivity

BasophilsBasophils RarestRarest of the of the

leukocytes (<0.5%)leukocytes (<0.5%) 10-12 10-12 m diameterm diameter Respond to allergic Respond to allergic

reactions (reactions (e.g., e.g., bee & bee & wasp stings, pollen)wasp stings, pollen)

Very granular; nucleus Very granular; nucleus often obscuredoften obscured

Live for about 2 weeksLive for about 2 weeks

Basophils are Basophils are very granularvery granular


Leukocytes Involved in Leukocytes Involved in Innate Immunity: Innate Immunity: CytotoxicityCytotoxicity

Natural Killer CellsNatural Killer Cells A specialized lymphocyteA specialized lymphocyte Attack virus-infected cellsAttack virus-infected cells Attack cancer cells (tumors)Attack cancer cells (tumors) NK cells recognize NK cells recognize

infected/defective cells via infected/defective cells via surface featuressurface features

Bind to target cells, release Bind to target cells, release chemicals (perforins) that chemicals (perforins) that lead to apoptosislead to apoptosis

An NK cell (N) attached to a "target" cell "T". The NK cell will kill the now helpless target cell quickly, by the injection of deadly perforin.


Leukocytes Involved in Leukocytes Involved in Acquired ImmunityAcquired Immunity

LymphocytesLymphocytes Very common in blood; Very common in blood;

20-40% of WBCs20-40% of WBCs Slightly larger than Slightly larger than

RBCs (~10 RBCs (~10 m)m) Dark-staining, circular Dark-staining, circular

nucleusnucleus Agranular; cytoplasm Agranular; cytoplasm

is transparentis transparent


Lymphocyte SpecializationLymphocyte Specialization Vertebrate lymphocytes take on specialized rolesVertebrate lymphocytes take on specialized roles Circulate through blood & lymph, concentrated in Circulate through blood & lymph, concentrated in

spleen & lymph nodesspleen & lymph nodes B & T cells bear ~100K antigen receptors (all the B & T cells bear ~100K antigen receptors (all the

same)same)

Lightchain

VV

C

C C

C

VV

Antigen-binding sites

Variable regions

Constant regions

C

V

C

V

T cell chain chainHeavy

chainsB cell

IgM IgM ReceptorsReceptors


Acquired Immunity ResponsesAcquired Immunity Responses Humoral ResponseHumoral Response

Dendritic cell (APC) engulfs pathogen, presents Dendritic cell (APC) engulfs pathogen, presents antibody via cell-surface protein (MHC class II)antibody via cell-surface protein (MHC class II)

Helper T cell binds to presented antigenHelper T cell binds to presented antigen APC releases cytokines to stimulate production of APC releases cytokines to stimulate production of

more “activated” T cellsmore “activated” T cells Activated B cells secrete antibodies, which immobilize Activated B cells secrete antibodies, which immobilize

pathogens, marking them for destruction by pathogens, marking them for destruction by macrophagesmacrophages

Cellular Immune ResponseCellular Immune Response A cell other than a leukocyte takes up and kills a A cell other than a leukocyte takes up and kills a

microbe, presents antigen on surface (MHC class I)microbe, presents antigen on surface (MHC class I) Cytotoxic (activated) T cell binds to presented Cytotoxic (activated) T cell binds to presented

antigen, releases perforins, lyses infected cell antigen, releases perforins, lyses infected cell

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PALOMAR COLLEGE Biology 201 Fundamentals of Biology II Rob Mustard Adjunct Faculty