Download VPB 553 Principles of Veterinary Immunology

Diseases of Immunity
2011 CL Davis
General Pathology
Paul W. Snyder, DVM, PhD
Purdue University
Acknowledgements
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Pathologic Basis of Veterinary Disease, 5th Ed
Veterinary Immunology, An Introduction 8th Ed
Immunology, Kuby, 6th Ed
The Immune System, Parham, 3rd Ed
Immunobiology, Janeway, 7th Ed
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Immunology
The study of the immune system and of diseases
that occur as a result of inappropriate or inadequate
actions of the immune system.
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The body’s defense system
pathogen
Physical and chemical barriers
- epidermis, mucosal epithelium
- pH of the stomach
- mucociliary apparatus
- lysozyme
Innate immunity
Adaptive immunity
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Innate Immunity – Cells
• Phagocytic cells
– Macrophages and neutrophils
• Dendritic cells – sense “danger”
– Not a unique population but rather a large
collection of subpopulations
• Mature into different functional profiles dependent
on the nature of the stimulus
– Activate naïve T lymphocytes - APCs
• Signal 1 = TCR - MHC/antigen peptide
• Signal 2 = CD28 - B7
• Cytokines
– IL-12 → TH1 response, NK cell activation
– IL-4, IL-5, IL-13 → TH2 response
Neutrophils
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Neutrophil migration
IL-8 (CXCL8)
C5a
LTB4
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NK cells
• 5- 15% of PBMC
• CD16 (Fc III R)
• CD56
• CD2
• IL-12 stimulates NK cells to
produce IFN → TH1
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NK Cells
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Receptors
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Activating
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C type lectin-like (KLR)
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Inhibitory
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Killer cell Immunoglobulin-like receptors (KIR)
FcgIII receptor (CD16)
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Recognize viral and stress induced proteins
ADCC
FasL
TLR 3 & 9
Species differences in MHC I specific receptors on
NK cells
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KIR – cattle, pigs, dogs, cats
KLR – mice, rats, horses
2010
Inhibitory vs activating Snyder
differences
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NK Cells
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Function
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Cytotoxicity
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Direct
Indirect – ADCC
Perforin & granzyme, granulysin, fragmentin
FasL (CD95)
Cancer cells and virally infected cells
2 subsets in humans
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NK1 → IFN g → macrophage activation
NK2 → IL13 → inhibits macrophage activation
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NK Cells
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Regulation
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Activated by Type I interferons ( & β) during viral
infections
IL-12 from activated macrophages & DCs activate NK cells
and enhances killing
Activated NK cells produce IFN g facilitating a TH1
IL-2 & IL-15 activate NK cell proliferation
IL-21 down regulates NK cells
NK T cells
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Properties of CTL & NK cells
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Early TH 2 → late TH1
NK dendritic cells
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Dendritic Cells
• Component of innate immunity
• Not a unique population but rather a large collection
of subpopulations located in lymphoid and nonlymphoid tissues
• 2 Main DC subsets
– Conventional (“myeloid”) DC
– Plasmacytoid DC
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Anti-viral immunity
TLR 7 & 9
Single stranded RNA (TLR7) and DNA viruses (TLR9)
Type I IFN ( and )
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Dendritic cells
Langerhans’ cell
Interstitial DC
Interdigitating DC
Plasmacytoid DC
Circulating DC
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Dendritic cells
• Important antigen presenting cells
– high expression of MHC II molecules
Paul Langerhan
– efficient in processing and presentation of antigen
• Examples:
– Langerhans cells in the epidermis
– Interstitial (eg. dermal) dendritic cells
– Interdigitating dendritic cells in the paracortex of the lymph
node and in the thymus
• Follicular dendritic cells
– in lymphoid follicles
– not bone marrow derived
– do not process antigen
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Antigen sampling by DC’s
• Macropinocytosis – sampling the extracellular
fluid
• Receptor-mediated endocytosis, clathrin
coated pits
– Fc receptors
– C’ receptors (CR3 and CR4)
– C-type lectin receptors (CLR’s)
– Scavenger receptors
• Phagocytosis
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Antigen sampling by DC’s
• DC cell ability to capture antigen is attributed
to:
– High endocytic capacity
– Anatomic location
• Skin
• Mucosal surfaces
• Spleen
• Unique strategy for sampling through
epithelial barriers
– CX3CR1, receptor for fractalline a chemokine on
the surface of intestinal epithelium
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DC activation
• Sense danger signals
– PAMPsPRRs TLR’s and CLR’s
• Mature into different functional profiles
dependent on the nature of the stimulus
• Intrinsic bias of DC subpopulations even
though very plastic
• Main LN homing chemokine receptor
– CCR7 which recognizes CCL19 (interdigitating DC)
and CCL21 (stromal cells) expressed in T cell areas
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DC activation
• Maturation process
–  expression of MHC-peptide complexes
–  expression of CD40, CD80 & CD86
– Cytokine synthesis
• Mature DC activate naïve T cells by delivering 3 signals:
– TCR – MHC/peptide
– CD28 – CD80/CD86
– T cell differentiation
» IL-12 → TH1 response, NK cell activation
» IL-4, IL-5, IL-13 → TH2 response
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DC & NK cell cross-talk
• NK cell role in process of DC maturation
– NK cells kill DC that do not acquire a mature phenotype
• Death receptor-mediated not granule exocytosis
– NK cells stimulate maturation of DC’s
• TNF
• IFN
– Specific action seems to be influenced by NK:DC ratios
• High ratio = kill
• Low ratio = stimulate maturation
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Follicular dendritic cells
• Stromal cells (not bone marrow-derived)
• Do not express MHC II
• Do not process antigen
• Display antigen in the form of immune
complexes
Attract B cells to lymphoid follicles
via CXCL13
Produce cytokines that influence B cell
maintenance
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Dendritic cell heterogeneity (mouse)
CD4-, CD8+
CD4+, CD8-
CD4-, CD8-
Spleen
23%
56%
20%
Mes. LN
19%
4%
63%
Skindraining LN
17%
4%
37%
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LC-type
CD4-, CD8lo
33%
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Innate Lymphoid Cells (ILCs)
• ILCs (non-T or B cells) develop in an Id2-dependent
pathway, additional transcription factors drive additional
subsets
– NK cells → cytotoxic and non-cytotoxic subsets
– Helper cells (IL-25  IL-33 induces)
• ILC2 cells → IL-5 & IL-13 → anti-parasite responses
– RORt cells (require IL-7)
• Lymphoid tissue-inducer cells (LTi) → LN formation
• ILC17 cells → IL-17A → neutrophils → extracellular bacteria
• ILC22 cells → IL-22 → extracellular bacteria
• Functions:
– Responses to infectious organisms
– Lymphoid tissue formation
– Tissue remodeling following damage
Innate Immunity – Polarized
Responses
• Similar to CD4+ TH subsets
– ILC2 promote TH2 responses and inflammation at
mucosal surfaces in conjunction with epithelial cells
• ILCs can be polarized toward restricted cytokine
profiles - plasticity
• Exogenous signals drive the plasticity
• Disease associations:
– Allergic diseases
– Inflammatory diseases like IBD
– Autoimmune diseases
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Recognizing first responders
RNA sensing
Noninflammasome NLRs
Regulation of adaptive immunity
by innate immunity
NLRP3 inflammasome a sensor
for metabolic danger
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Innate Immunity -Components
• Recognition molecules
– Pattern Recognition Receptors (PRRs)
• An ability to sense “danger” by cells other than T and B
lymphocytes
– Pathogen Associated Molecular Patterns (phagocytic)
– Damage Associated Molecular Patterns (sensor)
• PRRs
– Toll-like receptor (TLR) family
– Nucleotide oligomerization domain-like receptor (NLR)
family
– Retinoic acid-inducible gene I-like receptor (RLR) family
Innate Immunity - Components
• PRRs initiate signaling
– Initiate cascades for cytokine synthesis through
transcriptional regulation and posttranslational modifications
– Type 1 IFNs (IFN-α and IFN-β)
– IL-1 family cytokines (IL-1β and IL-18)
• Inflammasomes – intracellular sensors
– Cytosolic multi-protein complexes → activate
caspase-1 → cleave pro-inflammatory
cytokines into active forms
Pattern Recognition Receptors
• PRR’s are classified as secreted,
transmembrane and cytosolic forms
• Collectins and pentraxins are examples of
secreted PRR
– Bind microbial surfaces and activate complement
• TLR’s and C-type lectins are examples of
transmembrane PRR’s
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Pattern Recognition Receptors
• Cytosolic PRR’s
– Widely distributed, all nucleated cells
– Examples are:
• Retinoic-acid-inducible gene-1-like receptors (RLRs)
• Nucleotide oligomerization domain-like receptor
receptors (NLR’s)
• PRR’s sense “danger” or “stranger”
• Initiate adaptive immune responses and
regulate cell death (apoptosis)
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Pattern Recognition Receptors
• Cell-intrinsic recognition mechanisms
– Involve Type I inferferons
– Three members:
• Retinoic acid inducible gene-1 (RIG-1)
• Melanoma differentiation associated gene 5 (MDA-5)
• Laboratory of genetics and physiology gene 2 (LPG-2)
– Specifically detect RNA molecular patterns not normally
present in the cytoplasm
• Cell-extrinsic recognition mechanisms
– Allows uninfected cells to participate in immune responses
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Pattern Recognition Receptors
– Members of the NLR are central regulators of
immunity and inflammation
• Activate transcription factors like
– Nuclear factor κB (NF- κB)
– Interferon regulatory factor (IRF)
– Nuclear factor of activated T cells (NFAT)
• Some NLR members form multi-protein complexes
referred to as inflammasomes that activate caspase-1
• Caspase-1 cleaves pro-inflammatory cytokines like IL10 and IL-8
• Other NLR members are involved in inflammasomeindependent innate immune responses
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NLR proteins signal through different multicomponent signalsomes
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Toll-like receptors (TLR)
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Expressed on numerous cell types “sentinel cells”
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Constitutive and inducible forms
Link innate and adaptive immunity
TLR can partially substitute for T cell activation of B
cells
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Macrophages, mast cells, DC’s, mucosal epithelium,
hematopoietic stem cells…
Patients with immunodeficiency disease can produce limited
quantities of antibody
MyD88 KO mice have impaired IgM, IgG1 & IgG2c,
but not other isotypes
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Toll-like receptors (TLR)
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TLR4 KO mice have impaired IgM responses
Species differences in ligand specificity
Genetic polymorphisms within a species
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15 genes identified
“Innate autoimmunity”
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HSP, fibrinogen, DNA
RA and SLE
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Toll-like Receptors
TIR = toll/IL-1 receptor
MyD88 an IL-1 receptor associated kinase
(IRAK) a universal activator of NK-kB
Tumor necrosis receptor-associated
factor 6 (TRAF6)
Signal 1 - ↑ transcription
Signal 2 – inflammasome activation
of caspase-1
MyD88
TRAF6
MAPK
Pro-inflammatory mediators
COX-2
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PGE2
NOS2
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NO
Caspase-1
pro-TNF
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TNF
pro-IL-1
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IL-1
pro-IL-6
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IL-6
Innate Immunity - Functions
• Phagocytosis
– Phagocytic cells and opsonins (C3b, PAMPS)
• Inflammation
– Mediators (C3a, C5a, inflammatory cytokines)
• Regulation
– Cytokines polarize acquired immune responses
• Interactions
– Cross-regulation within innate immunity and to
acquired immunity
PAMPs
DAMPs
Inflammasomes
LUNG
Abestosis
COPD
Asthma
Pro-IL-1 → IL-1
METABOLISM
Type II Diabetes
SKIN
Allergy
Inflammatory Conditions
BRAIN
Alzheimer’s
Multiple Sclerosis
JOINTS
Rheumatoid Arthritis
Gout
HEART
Hypertension
CANCER
Mesothelioma
INTESTINE
Inflammatory
Bowel Disease
Innate (non-specific) immune system
• Controls infections during the time (5-7 days)
that is needed to engage the adaptive
immune system
• Activates and directs the adaptive immune
system, primarily through signals delivered by
dendritic cells.
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pathogens
viruses
bacteria
parasites
physical and chemical barrier
infection
tissue damage
innate immune system
dendritic cells
neoplasms
adaptive immune system
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Acquired Immune System
• Lymphoid cells
– T and B lymphocytes
• Antigen recognition molecules
– TCR, sIg (BCR), MHC molecules
• Effector functions
– B cells → Ig producing plasma cells
– CD8+ Cytotoxic T cells
– CD4+ T cells
• Helper T cells (TH)
• Regulatory T cells (Treg)
• TH 17
• Interactions
– Polarized responses
• based on cytokine profiles
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Recognition molecules of the adaptive
immune system
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B and T lymphocytes
B lymphocyte
T lymphocyte
specificity
immunoglobulin
T cell receptor
maturation
fetal liver
thymus
bone marrow
ileal Peyer’s patch
bursa of Fabricius
function
immunoglobulin regulation
secretion (plasma cytotoxicity
cells)
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Hematopoiesis
hemopoietic stem cell
interleukin-3, GM-CSF
IL-7
erythrocytes
platelets
macrophages
granulocytes
B
T
lymphocytes
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Hematopoiesis
Leukocytes
programmed cell death
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live cell
“neglect” - lack of receptor
stimulation or growth factors
activation of TNF-receptor
or Fas by ligand
bcl-2
mitochondrial damage
caspases
breakdown of proteins
apoptosis
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T lymphocytes
TCR
CD4+
T helper (TH)
TCRd
CD8+
cytotoxic T cell (CTL)
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T lymphocytes
TCR
CD4+
T helper (TH)
TCRd
MHC II
CD8+
MHC I
cytotoxic T cell (CTL)
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Cytotoxic function of CD8+ T cells
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Helper function of CD4+ T cells
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Superantigens
• Exotoxins
• V regions of
TCR & MHC II
• 5 - 20% of T
cells
• Cytokines
– TNF, IL-1
• Toxic-shock
syndrome
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Lymphoid Tissues
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Primary lymphoid tissues
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Generation of B and T lymphocytes
Antigen-independent proliferation
Include
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Thymus
Fetal liver, bone marrow
Secondary (peripheral) lymphoid tissues
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Initiation of antigen-specific immune response
Antigen-dependent proliferation
Include:
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Spleen (white pulp)
Lymph nodes
Peyer’s patches & lymphoid nodules
NALT, tonsils, BALT
Development of Immune System in the calf
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Thymus
HSC
(10-100 cells/day)
Death by neglect >80%
Negative Selection 5-10%
Positive Selection <5%
DN
DP
medulla
cortex
CD4
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(< 5%,
CD8
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6
10 /day)
Lymph node
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Lymphoid follicles
Dark zone - B cell proliferation, somatic hypermutation
Light zone – memory cells, plasma cell precursors, isotype switching
Mantle – mature naïve B cells
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Germinal center
• Proliferation of B cells
• Somatic mutation and selection
of high affinity B cells
• Isotype switching
• Memory cell induction
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Bursa of Fabricius
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Spleen
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Structure of spleen
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Dog
Rat
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Storage spleen
Thick capsule and
many trabeculae
Prominent smooth
muscle
Relatively poorly
developed white pulp
Dogs, cats, horses
Defense spleen
Well developed
lymphoid tissue
Less smooth muscle
Rats, mice, humans
Intermediate spleen
Cattle, swine
78
Peyer’s patches
Johannes Peyer
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Peyer’s patches
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Group I
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Ruminants, dogs & pigs
Ileal PP
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Primary lymphoid organ
Developed at birth and involutes at sexual maturity
Only B cells
Jejunal PP which persist
Group II
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Rabbits and rodents
Randomly distributed between IL and JE
Develop after birth and persist
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Intraepithelial lymphocytes
IEL
CD3
CD3+ (90%)
TCR (30-50%)
CD4+CD8+
CD4+CD8(5-8%)
TCRd (30-75%)
(5-8%)
CD4-CD8+
(20-40%)
CD4-CD8+
(30-60%)
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CD4-CD8(5-10%)
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