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MUCOSAL IMMUNITY - Columbia University · mucosal immunity alessandra pernis p&s 9-435 x53763...
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MUCOSAL IMMUNITY
Alessandra PernisP&S 9-435
CHALLENGES FACED BY THE MUCOSALSYSTEM
SPECIALIZATION OF CELLS INVOLVEDIN MUCOSAL IMMUNITY
ORGANIZATION OF THE MUCOSALIMMUNE SYSTEM
CLINICAL IMPLICATIONS
DEFINITIONS
MALT= MUCOSA-ASSOCIATEDLYMPHOID TISSUE
MALT is the highly specialized immune systemwhich protects mucosal surfaces. The lymphoidelements associated with different mucosalsites share organizational as well as functionalsimilarities. It is the largest mammalianlymphoid organ system and in an adult itcomprises approximately 80% of alllymphocytes.
COMPONENTS OF THE MUCOSA-ASSOCIATED LYMPHOID TISSUE
Gastrointestinal tract (GALT) Bronchial Tree (BALT) Nasopharyngeal area (NALT) Mammary gland Salivary and lacrimal glands Genitourinary organs Inner ear
THE CHALLENGES
MOST FREQUENT PORTAL OF ENTRY FOR HARMFULSUBSTANCES. THUS THE MALT HAS TO MOUNT ANEFFECTIVE RESPONSE AGAINST A VAST NUMBER OFPOTENTIAL PATHOGENS.
THE MUCOSAL MEMBRANES OF THE DIGESTIVETRACT MUST ALLOW FOR THE ABSORPTION OFNUTRIENTS BY THE HOST. THUS THE MALT MUSTREMAIN HYPORESPONSIVE TO AN ENTIRE ARRAY OFHARMLESS SUBSTANCES.
SPECIALIZEDCOMPONENTS OF MALT
B CELLS
HUMORAL RESPONSES ARE CENTRAL TO ANEFFECTIVE MUCOSAL IMMUNITY.
THE MAIN HUMORAL MEDIATORS OFSPECIFIC MUCOSAL IMMUNITY ARESECRETORY IgA AND, TO A LESSER EXTENT,SECRETORY IgM.
THE NORMAL INTESTINAL MUCOSACONTAINS AT LEAST 20 TIMES MORE IgA+THAN IgG+ LYMPHOCYTES.
CRITICAL FEATURES OFSECRETORY IgA
RESISTANCE AGAINST COMMONINTESTINAL PROTEASES
INABILITY TO INTERACT WITHCOMPLEMENT OR CELLS IN A WAY TOCAUSE INFLAMMATION
MECHANISMS OF PROTECTION BYSIgA AT MUCOSAL SURFACES
INHIBITION OF ADHERENCE VIRUS NEUTRALIZATION NEUTRALIZATION OF ENZYMES AND
TOXINS IMMUNE EXCLUSION AND INHIBITION OF
ANTIGEN ABSORPTION
FACTORS CONTROLLING IgA ISOTYPESWITCHING
APC
CD4
B BIgA-J
B7
CD28 TCRMHC II
ACTIVATIONCYTOKINESECRETION
CD40LCD40
TGF-β
ACTIVATION ISOTYPE SWITCHING
PROLIFERATIONDIFFERENTIATION
IL-2/IL-4
IL-5
IL-6
IL-10
FACTORS CONTROLLING THESECRETION OF IgA: THE J CHAIN
THE J CHAIN IS A 15 KD POLYPEPTIDE THAT ISDISULFIDE-BONDED TO THE TAIL-PIECES OF BOTH IgMAND IgA
IgA SECRETING B CELLS IN THE BONE MARROW DO NOTEXPRESS THE J CHAIN AND THUS SECRETE IgAMONOMERS
THE MAJORITY OF IgA PRODUCING B CELLS IN THEMUCOSA EXPRESS THE J CHAIN AND THUS PRODUCEDIMERIC IgA
THE J CHAIN STABILIZES THE MULTIMERS AND ITAPPEARS TO DETERMINE THE POLYMERIC IgA AND IgMSTRUCTURE WHICH ALLOWS POLYMERIC Igs TO COMPLEXWITH THE SECRETORY COMPONENT
FACTORS CONTROLLING THESECRETION OF IgA: THE SECRETORY
PIECE (POLYMERIC Ig RECEPTOR)
IgA-JIgA-J
LAMINA PROPRIA MUCOSALEPITHELIAL CELL
LUMEN
SECRETED IgA
PROTEOLYTIC CLEAVAGE
DIMERIC IgA
SECRETORY COMPONENTWITH BOUND IgA
ENDOCYTOSED COMPLEXOF IgA AND SECRETORY COMPONENT
T CELLS
TH1 OR TH2?
MUCOSAL TISSUES % CD3+ TCR %CD4+ TH1:TH2 CD4:CD8αβ γδ
INDUCTIVE SITES PEYER’S PATCHES
EFFECTOR SITES LAMINA PROPRIA
INTRAEPITHELIUM
25-35
40-60 >95 1-5 60 1:2-3 2:1
80-90 35-45 45-65 5-10 1:1 1:7-8
>90 1-5 60 1:1 2:1
LAMINA PROPRIA LYMPHOCYTES
LYMPHOCYTES WHICH ARE SCATTEREDDIFFUSELY THROUGHOUT THE LAMINAPROPRIA OF THE INTESTINE. (LAMINAPROPRIA=LAYER OF CONNECTIVE TISSUEBETWEEN THE EPITHELIUM AND THEMUSCULARIS MUCOSA)
LARGEST SINGLE T-CELL SITE IN HUMANS.MOST OF THE T CELLS WITHIN THELAMINA PROPRIA ARE CD4+.
INTRAEPITHELIAL LYMPHOCYTES (IELs)
IELs ARE LYMPHOCYTES WHICH AREINTERSPERSED BETWEEN THE COLUMNAREPITHELIAL CELLS OF THE VILLI IN THESMALL AND LARGE INTESTINE
IN HUMANS, MOST OF THE IELs ARE CD8+T CELLS. APPROXIMATELY 10% OF IELs AREγδ CELLS
BOTH THE γδ AND THE αβ TCR+ IELs SHOWLIMITED DIVERSITY OF T CELL
IELs EXPRESS A NOVEL INTEGRIN TERMEDHML-1 (human mucosal antigen 1).
FUNCTIONAL PROPERTIES OF IELs.
FIRST IMMUNE CELL LINE OF DEFENSE INTHE INTESTINE
DISPLAY CYTOTOXIC ACTIVITY SECRETE LARGE AMOUNTS OF CYTOKINES
ESPECIALLY IFN-γ AND TNF-α MODULATE THE KINETICS OF EPITHELIAL
CELL RENEWAL PLAY A REGULATORY ROLE IN TOLERANCE
TO DIETARY ANTIGENS
ORAL TOLERANCE
ORAL TOLERANCE
ORAL ADMINISTRATION OF A PROTEINANTIGEN MAY LEAD TO SUPPRESSION OFSYSTEMIC HUMORAL AND CELL-MEDIATEDIMMUNE RESPONSES TO IMMUNIZATIONWITH THE SAME ANTIGEN.
POSSIBLE MECHANISMS:– INDUCTION OF ANERGY OF ANTIGEN-
SPECIFIC T CELLS– CLONAL DELETION OF ANTIGEN-SPECIFIC
T CELLS– SELECTIVE EXPANSION OF CELLS
PRODUCING IMMUNOSUPPRESSIVECYTOKINES (IL-4, IL-10, TGF-β)
REGULATORY T CELLS(CD4+)
TH3 CELLS: A POPULATION OF CD4+T CELLSTHAT PRODUCE TGF-β. ISOLATED FROM MICEFED LOW DOSE OF ANTIGEN FOR TOLERANCEINDUCTION
TR1 CELLS: A POPULATION OF CD4+T CELLSTHAT PRODUCE IL-10. CAN PRODUCESUPPRESSION OF EXPERIMENTAL COLITIS INMICE
CD4+CD25+ REGULATORY T CELLS: APOPULATION OF CD4+T CELLS THAT CANPREVENT AUTOREACTIVITY IN VIVO.
REGULATORY T CELLS
CD8+SUPPRESSOR T CELLS: THE FIRSTIDENTIFIED POPULATION OF REGULATORY TCELLS THOUGHT TO BE INVOLVED IN ORALTOLERANCE. THEIR FUNCTIONS ANDCHRACTERISTIC HAVE NOT BEEN CLEARLYDEFINED
γδ T CELLS: STUDIES IN MICE INDICATETHAT THEY HAVE AN IMPORTANT ROLE INSOME MODELS OF ORAL TOLERANCE.
EPITHELIAL CELLS
Scanning electron microscopy of a single microdissected dome (a) of a murinePeyer's patch. The M cells are identified by their relatively short, dark brushborder; they are restricted to the dome epithelium (upper half in b). Crypts(arrows) are opening to the cleft between the dome and the neighboring villi.
From: Gebert et al., Am. J. Pathol. 154:1573, 1999
M CELLS
CHARACTERISTICS OF M CELLS
M ("membrane-like") CELLS ARE SPECIALIZEDEPITHELIAL CELLS WHICH OVERLIE LYMPHOIDFOLLICLES DOMES ALONG THE LENGTH OF THE SMALLAND LARGE INTESTINE.
STRUCTURAL FEATURES INCLUDE:– FEW SHORT IRREGULAR MICROVILLI– ABUNDANT ENDOCYTIC VESICLES– LOW LYSOSOMAL CONTENT– DISTINCTIVE GLYCOCALIX– BINDING SITES FOR SECRETORY IgA BUT NO SC– POCKETS IN THE BASOLATERAL SURFACE
FUNCTIONS OF M CELLS
ANTIGEN SAMPLING
PORTAL OF ENTRY FOR SELECTEDPATHOGENS
Dendritic cell-mediated transport of commensalbacteria in the gut
From: Kraehenbuhl and Corbett, Science 303:1624, 2004
Dendritic cells can sampleAntigen indirectly via M-celltranscytosis (right) ordirectly via processes thatextend across the epithelialbarrier (left). DCs presentantigen to B- and T-cells,either directly within thelamina propia or followingtrafficking to the regionallymph nodes
Role of CX3CR1 in Luminal Sampling by Gut DCs
From: Niess et al. Science 307:254, 2005
CX3CR1 is a chemokine receptor whose ligand is an unusual chemokine; rather than secreted, it is membrane-bound
ORGANIZATION OFMALT
PEYER’S PATCHES
ORGANIZED MUCOSAL LYMPHOID FOLLICLESWHICH LACK AFFERENT LYMPHATICS.
PEYER’S PATCHES ARE FOUND IN THE SMALLINTESTINE.
FOLLICLES SIMILAR TO PEYER’S PATCHESARE FOUND IN THE APPENDIX, IN THEREST OF THE GASTROINTESTINAL TRACTAND IN THE RESPIRATORY TRACT.
From: Iwatsukit et al., Histochem. Cell Biol. 117:1363, 2001
Anatomy of a Peyer’s Patch
INDUCTIVE LYMPHOEPITHELIALTISSUES:
PEYER’S PATCHES
M CELLS
B
B
T
MESENTERIC LYMPH NODES
APC
ACTIVATEDLYMPHOID FOLLICLE
THORACIC DUCT PERIPHERALBLOOD
T
T
T
B
B
B
B
EFFECTOR SITES:LAMINA PROPRIA AND
INTRAEPITHELIUM
DISTANT GUTMUCOSA
PERIPHERAL BLOOD OTHER EXOCRINE TISSUES
T4
T4
T8T8
APC
IgA-JBSC SIgA
CLINICAL IMPLICATIONS
IgA DEFICIENCY
IT IS THE MOST COMMON PRIMARYIMMUNODEFICIENCY
IT IS USUALLY DEFINED BY A SERUM IgACONCENTRATION OF LESS THAN 50 µg/ml
IgA DEFICIENT INDIVIDUALS OFTEN APPEARPERFECTLY HEALTHY AND ARE IDENTIFIED UPON SERVING AS BLOOD DONORS UPON UNDERGOING ANAPHYLACTIC SHOCK WHEN
RECEIVING BLOOD TRANSFUSIONS
CLINICAL MANIFESTATIONS OFIgA DEFICIENCY
INCREASED INCIDENCE OF INFECTIONS UPPER AND LOWER RESPIRATORY TRACT GASTROINTESTINAL
HIGHER INCIDENCE OF AUTOIMMUNEDISEASES
HIGHER INCIDENCE OF ALLERGIC DISEASES
HIGHER INCIDENCE OF CELIAC DISEASE
INFLAMMATORY BOWEL DISEASE(IBD)
IBD IS A CHRONIC, RELAPSING AND REMITTINGINFLAMMATORY CONDITION
TWO OVERLAPPING PHENOTYPES: CROHN’S DISEASE (CD), WHICH AFFECTS THE DISTAL
SMALL INTESTINE AS WELL AS THE COLON IN ATRANSMURAL MANNER
ULCERATIVE COLITIS (UC), WHICH PREDOMINANTLYAFFECTS THE COLON IN A SUPERFICIAL MANNER
THE ETIOLOGY IS UNKNOWN: ? DUE TO A DYSREGULATEDMUCOSAL IMMUNE RESPONSE TO UNKNOWN ANTIGENSPRESENT IN THE NORMAL, INDIGENOUS BACTERIAL FLORA– MUTATIONS IN NOD2 (A CYTOSOLIC RECEPTOR FOR
PATHOGENIC BACTERIAL SIGNALS) INCREASE THE RISK OF CDBY A FACTOR OF 20-40.
TRAF6ECSIT
DD
TIR domain MyD88
IRAK
NF-κB
MEKK1
IKK-γ
p65
extracellular space
cytosol
TAK
IKK-α IKK-β
MD2
CD14
Adaptor proteins
Kinases
IKK complex
p50I-κB
Receptor Complex
Similarity Between TLR-4 and NOD2
TIR = Toll/IL-1 receptorDD = Death domainIKK = I-κB kinase
RICK
CARD
LigandRecognition
NOD2
TLR-4
IBD: IMMUNOLOGIC FEATURES
CELL-MEDIATED IMMUNITY (ACTIVE CD): INCREASED NUMBER OF ACTIVATED MUCOSAL T
CELLS SECRETING IFN-γ (TH1) INCREASED MUCOSAL PRODUCTION OF CYTOKINES
THAT ACTIVATE TH1 CELLS (IL-12 AND IL-18) DEFECTS IN REGULATORY (IL-10 PRODUCING) T
CELLS
IBD: IMMUNOLOGIC FEATURES
HUMORAL IMMUNITY: MASSIVE INCREASE INTHE NUMBER OF PLASMA CELLS AND IN IgGPRODUCTION (IgG2 IN CD AND IgG1 IN UC)
IMBALANCE OF PRO-INFLAMMATORY (TNF-α,IL-1,IL-8, IL-12) AND ANTI-INFLAMMATORYCYTOKINES (IL-10, IL-4, IL-13)
IBD:EMERGING BIOLOGICTHERAPIES
INHIBITORS OF PROINFLAMMATORY CYTOKINES– Anti-TNF therapies: infliximab
ANTIINFLAMMATORY CYTOKINES– IL-10– IL-11
ANTI-LEUKOCYTE ADHESION THERAPIES– Anti-α4 integrin: Natalizumab ?
INHIBITORS OF TH1 POLARIZATION– Anti-IL-12– Anti-IL-18– Anti-IFN-γ
CELIAC DISEASE
CELIAC DISEASE IS A T CELL MEDIATEDIMMUNE DISEASE OF THE SMALL INTESTINETRIGGERED BY GLUTEN
MAJOR FEATURES: VILLOUS ATROPHY WITH A LYMPHOCYTIC
INFILTRATE INCREASED EPITHELIAL PROLIFERATION
WITH CRYPT HYPERPLASIA MALABSORPTION
Normal Celiac pt
CELIAC DISEASE: IMMUNOLOGICFEATURES
ANTIGEN: GLUTEN (gliadin and glutenins)
IT IS ASSOCIATED WITH HLA-DQ2 OR HLA-DQ8RESTRICTED LAMINA PROPRIA CD4+ T CELLS THATRECOGNIZE GLUTEN AND SECRETE INTERFERON γ (98% OFPEOPLE WILL CARRY THESE HAPLOTYPES)
GLIADIN IS A SUBSTRATE OF TISSUE TRANSGLUTAMINASE(TRANSFORMS POSITIVELY CHARGED GLUTAMINES TONEGATIVELY CHARGED GLUTAMIC ACID)
INCREASED B CELL ACTIVITY– ANTIBODIES AGAINST GLIADIN (IgA-AGA, IgG-AGA)– ENDOMYSIAL ANTIBODY (IgA-EMA)– TISSUE TRASGLUTAMINASE (IgA-tTG)
The CD4 side of the story
CELIAC DISEASE: IMMUNOLOGICFEATURES
IMPORTANTLY THE HALLMARK OF CELIAC DISEASE ISINTRAEPITHELIAL INFILTRATION BY CD8+ T CELLS– DIFFERENT FROM IBD– IELs ARE BELIEVED TO PARTICIPATE IN THE
PATHOGENESIS OF CELIAC DISEASE BY MEDIATING THEDESTRUCTION OF THE EPITHELIUM
– RECENT EVIDENCE POINTS TO THE FOLLOWINGSCENARIO: GLUTEN ALTERS EPITHELIAL CELLS OF PATIENTS WITH
CELIAC DISEASE LEADING TO PRODUCTION OF IL-15 ANDTO THE EXPRESSION OF NON-CLASSICAL MHC CLASS IMOLECULES. IL-15 IN TURN LEADS TO THE EXPRESSION OFRECEPTORS ON IELS FOR THESE NON-CLASSICAL MHCMOLECULES AND TO THE ACTIVATION OF THE IELS, WHICHTHEN KILL THE EPITHELIAL CELL
MUCOSAL VACCINES
VACCINES AGAINST MUCOSAL INFECTIONS MUSTSTIMULATE THE MALT IN ORDER TO BEEFFICACIOUS
BECAUSE OF SUBCOMPARTMENTALIZATION WITHINTHE MALT, VACCINES MUST BE ADMINISTERED BYTHE APPROPRIATE ROUTE
NONREPLICATING ANTIGENS ARE OFTEN RELATIVELYINEFFICIENT IN YIELDING STRONG AND LONG-LASTING MUCOSAL ANTIBODY RESPONSES
MUCOSAL VACCINES
NEW STRATEGIES FOR ANTIGEN DELIVERY: LIVE ATTENUATED RECOMBINANT BACTERIA AND
VIRUSES WITH KNOWN MUCOSAL TROPISM PROTECTIVE VEHICLES, E.G. LIPOSOMES AND
BIODEGRADABLE MICROSPHERES MUCOSAL LECTIN-LIKE MOLECULES ENDOWED WITH
IMMUNOSTIMULATORY PROPERTIES, E.G. CHOLERATOXIN
MUCOSAL IMMUNOTHERAPY
STRATEGY TO ATTEMPT TO TREATILLNESSES RESULTING FROM IMMUNEREACTIONS AGAINST AUTOANTIGENSENCOUNTERED IN NONMUCOSAL TISSUES
HUMAN TRIALS HAVE BEEN CONDUCTED INMULTIPLE SCLEROSIS, RHEUMATOIDARTHRITIS, UVEORETINITIS, AND TYPE IDIABETES