Transcript Week 9: Today`s Program

Biology 201
Fundamentals of Biology II
Rob Mustard
Adjunct Faculty
PALOMAR COLLEGE
Leukocytes & Immune Response


Blood cells are one of the “fluid” Connective
Tissues
Red blood cells
(erythrocytes)
 Mammalian
RBCs lack
nuclei and mitochondria
 ~7 m diameter

White blood cells
(leukocytes)
 Giemsa
stain to
differentiate WBCs
6-7 million erythrocytes / ml3
7,000 leukocytes / ml3
PALOMAR COLLEGE
Immune Response Modes

Innate Immunity
 Rapid
(and general) response to a broad
range of microbial invasion

Acquired (Adaptive) Immunity
 Secondary
(and highly-specific) response to
previously-encountered pathogens

Vertebrates have both forms of immuneresponse mechanisms
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Innate Immunity

External defenses include:
 Skin:
impenetrable to most viruses & bacteria
 Mucous: viscous fluid that traps microbes
 Cellular secretions: sebaceous (oil) & sweat
glands reduce skin’s pH to 3-5; lysozyme
digests Gram + cell walls

Internal defenses begin after bacteria
invade, typically through a break in skin or
other epidermal layer
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Inflammatory Response

Tissue damage from physical injury leads to
cascade of chemical signals
 Histamine,
stored in mast cells in connective
tissue
 Nearby capillaries become dilated and leaky,
allowing passage of macrophages and increased
blood flow
 Increased local blood supply leads to redness,
heat and swelling (inflammation)
 Macrophages move out into damaged tissues, in
interstitial spaces between cells
 Nonspecific Inflammatory Response
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Leukocytes Involved in
Innate Immunity: Phagocytes

Neutrophils
 60-70%
of all leukocytes,
live only a few days
 Big: 12-15 m (2x
erythrocytes)
 Nucleus has 2-5 lobes
(polymorphic)

Neutrophils are granular
Monocytes
 5%
of all leukocytes
 Biggest: 20 m
 Lighter, “frothy” horseshoeshaped nucleus
Monocytes are agranular
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Leukocytes Involved in
Innate Immunity: Phagocytes

Eosinophils
 Rare
in blood smears (2-4%)
 Big: 12-15 m (same size as
Neutrophils)
 Nucleus has 2 lobes

Dendritic Cells
 Patrol
Eosinophils are granular
interstitial spaces of
skin & mucosal membranes
 Phagocytize invaders,
process & present antigen
material (APCs)
 Activate acquired immune
system
PALOMAR COLLEGE
Leukocytes Involved in Innate
Immunity: Hypersensitivity

Basophils
 Rarest
of the
leukocytes (<0.5%)
 10-12 m diameter
 Respond to allergic
reactions (e.g., bee &
wasp stings, pollen)
 Very granular; nucleus
often obscured
 Live for about 2 weeks
Basophils are very granular
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Leukocytes Involved in
Innate Immunity: Cytotoxicity

Natural Killer Cells
A
specialized lymphocyte
 Attack virus-infected cells
 Attack cancer cells (tumors)
 NK cells recognize
infected/defective cells via
surface features
 Bind to target cells, release
chemicals (perforins) that
lead 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.
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Leukocytes Involved in
Acquired Immunity

Lymphocytes
 Very
common in
blood; 20-40% of
WBCs
 Slightly larger than
RBCs (~10 m)
 Dark-staining, circular
nucleus
 Agranular; cytoplasm
is transparent
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Lymphocyte Specialization



Vertebrate lymphocytes take on specialized roles
Circulate through blood & lymph, concentrated in
spleen & lymph nodes
B & T cells bear ~100K antigen receptors (all the
same)
Antigenbinding sites
IgM
Receptors
Variable
regions
Light
chain
C C
B cell
Heavy
chains
Constant
regions
 chain
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V
V
C C
b chain
T cell
Acquired Immunity Responses

Humoral Response
 Dendritic
cell (APC) engulfs pathogen, presents
antibody via cell-surface protein (MHC class II)
 Helper T cell binds to presented antigen
 APC releases cytokines to stimulate production of
more “activated” T cells
 Activated B cells secrete antibodies, which immobilize
pathogens, marking them for destruction by
macrophages

Cellular Immune Response
A
cell other than a leukocyte takes up and kills a
microbe, presents antigen on surface (MHC class I)
 Cytotoxic (activated) T cell binds to presented
antigen, releases perforins, lyses infected cell
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Questions??
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