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Microbes and Allergic Disease
Cathryn Nagler-Anderson
Massachusetts General Hospital
Harvard Medical School
1. Examine what we know about how
the body discriminates between harmful
pathogens and innocuous foreign
substances (antigens).
2. Introduce the mucosal immune
system, the portal through which most
foreign substances and microbes enter
the body.
3. Present some work from our
laboratory on the influence of intestinal
microbes on allergic disease.
There are two arms to the immune
response to any foreign substance
(antigen) entering the body:
the innate immune response
the adaptive immune response
Innate Immune Response
• rapidly deployed - first line defense
• encoded in genome - conserved from
flies to humans
• broad recognition of microbial“patterns”
• no memory of past encounter with
antigen
Adaptive Immune Response
• exquisitely specific recognition
of millions of different potential antigens
• requires gene rearrangement to generate
antigen specific receptors
• long-term memory of past antigen
encounter
Pattern recognition receptors (PRR) of the
innate immune system see pathogen
associated molecular patterns (PAMPS)
PAMPS are typically highly conserved,
essential components of microbial structure
or metabolism
The Toll-like receptor (TLR) family of
Pattern Recognition Receptors
Peptidoglycan (G+)
Lipoprotein
Lipoarabinomannans
Zymosan (Yeast)
GPI protein
TLR-6
TLR-2
LPS(G-)
RSV F
TLR-1 CD14 MD-2 TLR-4
dsRNA
TLR-3
Flagellin
TLR-5
Bacterial
CpG DNA
TLR-9
Based on Nat. Rev. Immunol. 2001; 1: 135
Antigen specific receptors on
T cells and B cells characterize the
adaptive immune response.
T cells - cell mediated immunity
B cells - antibody mediated (humoral)
immunity
T cells see peptide fragments of antigen
presented by MHC proteins on antigen
presenting cells
T cell receptor
MHC
Antigen presenting
cell (APC)
T cell
Two signals are required for T cell activation
MHC
TCR
Costimulatory molecules
on APC provide the
second signal
Adjuvant - a substance that activates the
innate immune system to produce signals
required for an adaptive immune response
Adjuvants potentiate T cell immunity by:
1. Enhancing expansion of antigen
specific T cells
2. Altering antigen presentation (upregulation
of costimulation).
3. Influencing differentiation of T cell subsets.
Adjuvants
Cathryn
NaglerAntigen
Anderson:
presentation without activation of the innate
immune system leads to non-responsiveness (anergy)
Pathogens
TLRs
Antigen
presentation
T
APC
TH1
Costimulatory
molecules
IL-12, IL-18
Soluble Proteins
TLRs
Antigen
presentation
T
APC
Costimulatory
molecules
IL-12, IL-18
Anergy
IFN-g
+
CD4 T helper cells
Th1
Th2
IL-2
IFN-g
TNF
IL-4
IL-5
IL-13
cell mediated
responses
help antibody
responses
Most immune responses have both a Th1 and Th2
component. The T cell response to some infectious
agents becomes polarized to one Th subset.
Degree of polarization
Degree of polarization
Th
Th11
Bacteria
Gram - (tuberculosis)
negative
Viruses
(measles)
bacteria
Th
2
Th2
Helminthic
Helminthic
Parasites
(worms)
parasites
Work in our laboratory has
examined the influence of two types
of microbes on the development of
food allergy
•Intestinal worms (helminths)
•Intestinal (commensal) bacteria
Antigens enter through mucosal surfaces
Right subclavian vein
Superior vena cava
Liver
Stomach
Mesenteric nodes
Peyer’s patches
Appendix
Oesophagus
Trachea
Left subclavian vein
Mediastinal lymph nodes
Lungs
Heart
Spleen
Thoracic duct
Large intestine
Small intestine
Gut-associated lymphoid tissue
Peyer’s patch
Villus epithelium
The induction of nonresponsiveness to orally
administered antigens
(including food) is called oral
tolerance.
Microbes living in the gut
influence the immune response to a
food antigen through their
interactions with the innate and
adaptive immune system.
Life cycle of an intestinal worm,
Heligmosomoides polygyrus
24 - 36 h
L1
Eggs
L4 9 - 11 Days
wall
Adult
Lumen
Adult
Small Intestine
L3
2 - 6 Days
L2
H. polygyrus
establishes
a chronic, noninvasive
niche in the
intestinal
lumen
From Telford et al, Parasite
Immunol. 1998: 20, 601
QuickTime™ and a
GIF decompressor
are needed to see this picture.
Oral Ag primes for a Th2 response
in helminth infected mice
pg/ml (+SE)
2000
6000
IFN-g (Th1)
5000
1500
IL-5 (Th2)
4000
1000
3000
2000
500
1000
0
0
PBS OVA
fed fed
Non-infected
PBS OVA
fed fed
Infected
PBS OVA
fed fed
PBS OVA
fed fed
Non-infected Infected
Shi et al, J. Immunol. 1998, 160: 2449
Response to different forms of antigen presented to the GALT
leads to systemic nonresponsiveness or immunity
Soluble Ag
Ag + adjuvant, microbes
T cell proliferation and activation
T cell proliferation and activation
1st Ag challenge
Antigen specific clonal expansion
Antigen specific reduction in
proliferative capacity
Subsequent challenges
Profound reduction in
proliferative capacity;
functional non-responsiveness
due to failure to clonally expand
antigen specific clones and/or cell death
Clonal expansion enhanced
by each antigen challenge
leads to productive immune
response
The relationship between infection and allergic disease
In developed countries:
In developing countries:
High incidence of
allergic disease
Low incidence of
allergic disease
Low incidence of
infectious diseases (Th1)
High incidence of
infectious diseases (Th1)
Low infection with
worms (helminths)
Allergic disease
(Th2)
Helminth Infection
(Th2)
High infection with
worms (helminths)
Microbial Infection
(Th1)
TLR signaling regulates the development of Th1 and Th2 cells
Pathogens
IFN-g
Antigen
presentation
TLRs
T
APC
TH1
IFN-g
Costimulatory
molecules
IL-12, IL-18
Helminths, Allergens
? ?
TLRs
APC
?
IL-4
Antigen
presentation
T
Costimulatory
molecules
IL-4, IL-10 ?
TH2
IL-4, IL,5
IL-13
The Hygiene Hypothesis
Allergy and asthma have increased during the last
20-50 years due to reduced exposure to childhood
bacterial and viral infections brought about by
improvements in vaccination and sanitation.
In the absence of these Th1 polarizing stimuli
mucosal immune responses fail to overcome their
inherent Th2 bias and become slanted in the
direction of allergy.
Does helminth infection induce an allergic response?
QuickTime™ and a
Photo - JPEG decompressor
are needed to see this picture.
Interleukin-13
(N. Engl. J. Med. 2001, 344: 30)
A model for food allergy
An allergic response to a food antigen
(peanut) can be induced in C3H/HeJ
mice by repeated oral administration
of peanut plus a mucosal adjuvant
(cholera toxin)
An allergic response is measured by:
• 1. Symptoms of anaphylaxis
(itching,wheezing, labored
respiration, convulsions)
•2. Elevated levels of plasma
histamine
•3. Induction of peanut specific IgE
Helminth infection (HP) does not induce
an allergic response to a food antigen
10000
400
7500
300
5000
200
2500
100
∆ - Histamine ng/ml
Peanut IgE ng/ml
500
0
0
PBS
PBS/CT
PN
PN/CT HP/PBS PN/HP
Bashir et al J. Immunol. 2002, 169:3284
1000
4000
750
3000
500
2000
250
1000
∆ - Histamine ng/ml
Peanut IgE ng/ml
Helminth infection protects against peanut allergy
0
0
PN/CT
PN
HP/PN/CT HP/PBS PBS/CT
Bashir et al J. Immunol. 2002, 169:3284
Counter-regulation hypothesis
Organ specific autoimmune disease
TH1
INFLAMMATION
TH2
Commensal gut
Microflora
Protozoa
Viruses
Bacteria
IL-10
(TGF-b)
Helminths
Viruses
Bacteria
Protozoa
CD4+ regulatory T cells
CD8+ T cells
B cells
Dendritic cells
Monocytes/
macrophages
Epithelial cells
Allergic disease
Inhibitory
Commensal gut
Microflora
Adapted from Wills-Karp, et al
Nat.Rev.Immuno.1, 2001:69
Mice lacking TLR-4, the receptor for bacterial
LPS, are highly susceptible to an allergic
response to peanut plus CT
3000
7500
2000
5000
1000
2500
0
0
D - Histamine
PN-IgE ng/ml
10000
Removal of gut bacteria by antibiotic treatment induces an
allergic response to peanut in TLR-4 positive mice
3000
2000
2000
1000
0
1000
0
D - Histamine
PN-IgE ng/ml
3000
Allergy is induced in the absence of TLR-4
signaling by luminal bacteria
T
T
T
B
B T
T
B B
B
B
IL-10
Tr1
Tr1
IL-10
Tr1
TLR-4
IgE
IFN-g
Immature (or
mature?) DC
in GALT
(PP, MLN?)
Th3
Th3
Th3
TGF-b
TGF-b