Transcript Presentation

Conflict of Interest Statement
Anthony DeFranco
Identified conflicts of interest
-I am on the Scientific Advisory Board of UCB-Pharma, a
pharmaceutical company that sells anti-inflammatory drugs (one
of the five approved TNF blockers) and anti-histamines.
Additional immunology-related therapeutics are in late phase
clinical testing
-My wife and I own stock in several biotechnology companies
that make anti-inflammatory drugs and/or are currently in late
phases of testing such drugs
Management of conflicts of interest
-I will not comment on relative advantages or disadvantages of
specific products or potential products made by these
companies vs. competitive products of other companies
Inflammation and Innate Immunity (part I)
• Inflammation
• Innate immunity and the initial response to
infection
• Cytokines that induce inflammation and direct
inflammatory cells
• Recognition of microbes by Toll-like receptors
(TLRs) and other innate recognition elements
• Inflammation and recruitment of phagocytes
• Uptake and killing of bacteria by phagocytes
• Innate immunity against fungi, helminths, at
mucosal epithelium
Inflammation
QuickTime™ and a
decompressor
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Source: Wikipedia
Inflammation
“rubor et tumor cum calore et dolore”
(redness and swelling with heat and pain)
--Cornelius Celsus in De Medicina, 1st century
A.D.
later “functio laesa” (disturbance of function)
was added
Inflammation
“rubor et tumor cum calore et dolore”
(redness and swelling with heat and pain)
--Cornelius Celsus in De Medicina, 1st century
A.D.
later “functio laesa” (disturbance of function)
was added
Inflammation is an adaptive response to noxious
conditions (infection and tissue injury)--an attempt
to restore homeostasis
Inflammation
• Inflammation can be induced by immune recognition of infection
or tissue damage (usually good)
• Inflammation can be induced by immune recognition that is
hypersensitive to environmental components or autoinflammatory
or autoimmune (=disease)
Inflammation
• Inflammation can be induced by immune recognition of infection
or tissue damage (usually good)
• Inflammation can be induced by immune recognition that is
hypersensitive to environmental components or autoinflammatory
or autoimmune (=disease)
• Acute inflammation: influx of white blood cells and fluid from
blood to fight infection and aid tissue repair
• Chronic inflammation: inducer of inflammation is not removed
– Leads to tissue damage and loss of tissue function (joint
destruction, lung fibrosis, etc.)
– Current view: aggressively fight inflammation in certain
chronic diseases to decrease/delay progressive loss of
function
Inflammation
•
Inflammation can be induced by immune recognition of infection or
tissue damage (usually good)
•
Inflammation can be induced by immune recognition that is
hypersensitive to environmental components or autoinflammatory or
autoimmune (=disease)
•
Acute inflammation: influx of white blood cells and fluid from blood to
fight infection and aid tissue repair
•
Chronic inflammation: inducer of inflammation is not removed
– Leads to tissue damage and loss of tissue function (joint destruction,
lung fibrosis, etc.)
– Current view: aggressively fight inflammation in certain chronic
diseases to decrease/delay progressive loss of function
•
Current research suggests that inflammation may play an important role
in common chronic diseases including atherosclerosis, type 2 diabetes,
neurodegeneration, and cancer
Immune sentinel cells in the tissues:
dendritic cells
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Green= dendritic cells
Blue= nuclei of all cells
Langerhans cells (epidermal dendritic cells) in the skin
WJ Mullholland et al. J. Invest. Dermatol. 126: 1541, 2006.
Infection leads to
production of inducers
of inflammation
or dendritic cell
Inflammatory mediators:
Complex and many, but include:
Lipids and
Proteins (cytokines/chemokines)
TNF
Others
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Cytokines
•“Cytokines” are soluble protein mediators secreted by immune
cells (mostly) that act on other cells to regulate their activity;
many are called “interleukins” (IL-1, IL-2, etc.) (note:
sometimes exist in cell-bound forms)
•Cytokines have many functions, we’ll focus on a few central
functions of some key cytokines (see “Cytokine primer” in
syllabus)
•Name of a cytokine often doesn’t reflect its most important
function (example: TNF stands for “tumor necrosis factor” but
main function is to induce inflammation)
•A subfamily of cytokines primarily functions in directing
migration of cells, these are called “chemotactic cytokines” or
“chemokines”
Chemokines have systematic names: CCL1, 2, … and CXCL1, 2, …
(but older names sometimes used, including IL-8)
The Initial Response to
Infection: Innate Immunity
• Recognition of types of molecules (“molecular patterns”) made
by microbes or viruses but not by our cells by innate immune
receptors
• Alternatively, recognition of tissue damage and cell death,
which are often associated with infection (“danger”).
• Rapid mobilization of leukocytes to the site of infection or
damage and influx of plasma into the tissue site (=inflammation)
• Recruited innate immune cells kill microbes or virally infected
cells. Immune cells also can promote tissue repair but when
dysregulated can exacerbate tissue injury
• Also, innate recognition promotes the adaptive immune
response, which is slower but more powerful
Cytokines and Inflammation
• Macrophages or DCs stimulated via innate immune
receptors make pro-inflammatory cytokines, especially
TNF (Tumor necrosis factor), IL-1, and IL-6
• TNF and IL-1 signal to endothelial cells to make them:
– Leaky to fluid (influx of plasma; containing
antibodies, complement components, etc.)
– Sticky for leukocytes, leading to influx of first
neutrophils, later monocytes, lymphocytes
• IL-6 promotes adaptive immune responses and has
systemic effects (“acute phase response” of liver,
including C-reactive protein or CRP; levels used
clinically as an indication of systemic inflammation)
Leukocyte recruitment to sites of inflammation
or DC
See Abbas and Lichtman Fig. 2-7
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decompressor
are needed to see this picture.
Note: molecular details of leukocyte extravasation will be
covered in lecture Thursday
Inflammation: Neutrophils vs. Monocytes
• Acute inflammation is initially characterized as rich in
neutrophils; later it is more monocytes and lymphocytes. This is
controlled by which chemokines are expressed by the endothelial
cells.
• Neutrophils are dedicated to killing microbes and are shortlived. They often damage host tissue as a byproduct.
• Monocytes are multi-potential, depending on cytokine signals:
+IFN-g: assume a vigorous killing phenotype similar to
neutrophils
+IL-4: “alternatively activated macrophages”; tissue repair,
barrier immunity
+IL-10: assume a wound-healing type phenotype (to clean up
after infection is cleared)
Anti-Inflammatory Therapeutics
• NSAIDs: inhibitors of inflammation and fever (block
prostaglandin synthesis)
• Glucocorticoids are also potent anti-inflammatory drugs;
natural systemic anti-inflammatory mechanism
• Agents that block TNF are effective in treating
rheumatoid arthritis, Crohn’s disease, etc.
• Agents that block IL-1 are less effective for these
diseases but are useful for some genetic inflammatory
diseases
How is infection first recognized by the
immune system?
• What is seen by innate immunity?
– Types of molecules made by microbes, but not by our cells
“Pathogen-associated molecular patterns” PAMPs
– Molecules released from necrotic cells, tissue damage
(“damage-associated molecular patterns” DAMPs). (Note: tissue
damage can also be recognized by pain neurons, which can promote
inflammation)
• What mediates the recognition?
– Diverse recognition elements; 4 key families of cellular
receptors:
• Toll-like receptors (TLRs)
• C-type lectin receptors (CLRs)
• RigI-like receptors (RLRs)
• NOD-like receptors (NLRs)
Innate recognition outside the cell or in endosomes:
TLRs and CLRs
TLR4
recognizes
LPS
Surface CLRs
carbohydrates
TLRs induce inflammatory
cytokines (+ interferon)
Endosomal TLRs recognize
nucleic acids (mostly from virus
particles). Localization in
endosomes is thought to aid
discrimination between virusderived and endogenous nucleic
acids
CLRs detect mostly
carbohydrates (fungi
especially); also recognize
dead host cells; induce
cytokines
Modified from Abbas and Lichtman Fig. 2-2
Sepsis Syndrome: very bad
(too much of a good thing)
• Bacterial septicemia leads to activation of TLRs on
monocytes in the blood, DCs in spleen
• Systemic release of TNF and IL-1 leads to
“inflammation” all over the body
• Shock from loss of blood pressure (vasodilation and
leakage of fluid into tissues)
• TLRs also induce coagulation (via tissue factor)
– Current therapy with some efficacy: “activated protein C”:
promotes fibrinolysis, breaks down thrombi
• The combination of effects frequently leads to multiorgan failure and death
Innate recognition in the cytoplasm:
NLRs and RLRs
Modified from Abbas and Lichtman Fig. 2-2
Inflammatory cytokines
Peptidoglycan
(RLRs)
Secrete anti-microbial
peptides into lumen of
crypts of sm. intest.
Engulfment of bacteria
invading the cytoplasm
(autophagy)
Common alleles of NOD2 are a genetic
risk factor for Crohn’s disease
•Several moderately common alleles of the NOD2 gene
(7% of total alleles) increase susceptibility to Crohn’s
disease (a form of inflammatory bowel disease)
•Two copies of these alleles increase susceptibility by 40X
•Mechanism: most evidence indicates these are loss-offunction alleles; unknown which function of NOD2 is most
relevant
Processing of IL-1 and related
cytokines: an important regulatory step
•Some “NLRs” assemble to form the “inflammasome” which
proteolytically processes IL-1 and related cytokines (IL-18) to
their active, secreted forms.
•Inflammasome in activated by cellular stress or recognition of
microbial components in the cytoplasm
Processing of IL-1 and related
cytokines: an important regulatory step
•Some “NLRs” assemble to form the “inflammasome” which
proteolytically processes IL-1 and related cytokines (IL-18) to
their active, secreted forms.
•Inflammasome in activated by cellular stress or recognition of
microbial components in the cytoplasm
•Genetic periodic fever syndromes are due to activating mutations
in the inflammasome (active when it shouldn’t be)
•Inflammasome is activated by some types of small crystals that
can be phagocytosed by macrophages, important role in Gout
The Inflammasome activates caspase 1
in response to cellular insults
Phagocytosed crystals
Bacterial pore-forming toxins
Efflux of K+
Bacterial flagellin
Other insults/stresses
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Several different NLRs can form
inflammasomes (shown is NLRP3/NALP3)
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Inducers of Inflammation
•Microbe PAMPs recognized by TLRs, NOD1/2 or CLRs: DCs,
macrophages makeTNF and IL-1
•Virus infections: infected cells, pDCs make IFN/ (type 1)
•Tissue damage (cell necrosis etc.): “DAMPs” activate DCs,
macrophages via TLRs, CLRs, inflammasomes (other receptors?)
•Complement fragments (innate activators or IgM or IgG +
antigen)
•Mast cell activation (IgE+allergen or innate mechanisms: release
histamine, leukotrienes, cytokines): eosinophil-rich inflammation
(“type 2 immunity”)
•Effector T cells responding to antigen (TNF + other cytokines;
chemokines)
Negative Regulation of Inflammation
•Cells responding to innate stimuli stop making
inflammatory mediators after short time period and
convert to making anti-inflammatory lipids (resolvins, etc.)
and anti-inflammatory cytokines (IL-10, TGF-)
•Killing the infectious agent and removal of the dead cells,
debris, crystals, etc. will stop stimulation of incoming
inflammatory cells
•Systemic elevation of inflammatory cytokines (esp. IL-1)
in severe infections induce production of glucocorticoids,
which are anti-inflammatory (also increased by stress)
•Regulatory T cells are also anti-inflammatory, both by
blocking effector T cells and by inhibiting innate cells
Phagocytosis and Killing of Microbes
Abbas and Lichtman Fig. 2-9
Phagocytosis and Killing of Microbes
Key Concepts related to phagocytosis:
1.
Opsonization: soluble immune
recognition elements tag a particle
for phagocytosis (opsonins include:
Mannose-binding lectin, C3b, IgG,
etc.)
2.
Interferon-g from NK cell or Th1 cell
promotes killing of internalized
microbes by monocytes/macrophages
3.
Killing mechanisms: ROI, NO,
proteases, anti-microbial peptides
Abbas and Lichtman Fig. 2-9
Phagocytosis and Killing of Microbes
Key Concepts related to phagocytosis:
1.
Opsonization: soluble immune
recognition elements tag a particle
for phagocytosis (opsonins include:
Mannose-binding lectin, C3b, IgG,
etc.)
2.
Interferon-g from NK cell or Th1 cell
promotes killing of internalized
microbes by monocytes/macrophages
3.
Killing mechanisms: ROI, NO,
proteases, anti-microbial peptides
Genetic defects in phagocyte
oxidase components: “chronic
granulomatous disease”
Abbas and Lichtman Fig. 2-9
Innate Immunity against fungal
pathogens
• CLRs are key innate recognition elements for
fungi/yeast (TLRs can also play a role)
• Neutrophils are important for killing most fungal
pathogens
• Some fungal pathogens can establish
intracellular infections (like some bacterial
pathogens): interferon-g is important for
defense; often also NO
Innate Immunity against helminths
• Often multicellular parasites induce a “type 2”
inflammation characterized by influx of eosinophils and
basophils instead of neutrophils and monocytes
• This type of inflammation is also seen in asthma and
allergies, as will be discussed later in the course and can
be propagated by Th2 adaptive immunity and/or IgE
• Innate recognition is not yet understood, may include
foreign polysaccharides (chitin), proteases, tissue
damage
• In some parasitic worm infections inside tissue, bacteria
in the gut/feces of the worm stimulate TLRs and
neutrophil-rich inflammation, which can cause pathology
(African river blindness)
Innate Immunity and Mucosal Epithelium
• Microbes are tolerated outside mucosal epithelium when
consistent with its function (colon; upper airways)
• Efforts to keep microbes out of some mucosal epithelial
regions (small intestines and small airways)
• Mechanisms include: actions of some surfactant proteins
in lungs (bind to foreign polysaccharides); secretion of
anti-microbial peptides by Paneth cells in crypts of small
intestines; secretion of mucus by goblet cells; g T cells
in epithelial tissue; IgA
• IL-13 is an important cytokine promoting mucus secretion
Tomorrow: Innate Immunity to Viruses
REMINDER:
The 1PM session is a live patient interview
session, so be here promptly by 1:10 and no
electronics or eating food when patient is
on stage
Patient Confidentiality must be maintained