Transcript Slide 1

12.
MUCOSAL IMMUNITY
MUCOSAL IMMUNE SYSTEM
 Protect mucous membranes from pathogens
 Prevent the development of self-damaging
inflammatory immune responses against harmless
environmental antigens
 Transport of antigens across mucosal surface M-cells
HUMORAL MUCOSAL RESPONSES
 Massive production of IgA (under the influence of
TGF-, IL-10, IL-4 in mucosal lymphoid tissues)
 Transport of IgA across epithelial cells on the
mucosal surface: Transcytosis; poly-Ig-receptor;
secretory component
 IgA in mother milk (newborn human does not
have own antibodies; serum contains only small
amounts of antibodies obtained transplacentary
from the mother)
CELL MEDIATED MUCOSAL RESPONSES
 Intraepithelial T-lymphocytes
 T-lymphocytes in lamina propria,
 Peyer’s plaques
CHARACTERISTIC FEATURE:
Mucosal immunization usually results in induction of
„tolerance“ (suppression of TH1, TC; stimulation of TH2 resp.
TH3 - IgA)
Suppressive (anti-inflammatory) cytokines
13.
TRANSPLANTATION
TRANSPLANTATION OF TISSUES AND
ORGANS
BASIC TERMS
 Donor, recipient, “graft“, rejection
 Grafts genetically identical with the recipient are
syngeneic
 Grafts from genetically non-identical donor of the
same species are allogeneic
 Grafts from a different species donor are
xenogeneic
SUPPRESSION OF TRANSPLANTATION
REJECTION REACTION
- Choice of genetically related donors (best - relatives)
- Immunosupression (cyclosporin A; corticosteroids;
antibodies to T-lymphocytes; irradiation)
- Ideal: induction of tolerance
- Xenotransplantation – possibly real; genetically modified
animals (baboons, pigs)
IMMUNE “PRIVILEGED“ ORGANS, TISSUES
Isolated from cells of immune system
- Anterior eye chamber
- Central nervovous system
- (Developing foetus)
Defense system of brain – microglial cells
(a form of tissue macrophages)
-
Active mechanisms – FasL
(destruction of activated T-cells
attacking a privileged tissue)
- Privileged sites vs. tissues
- Th2 x Th1. PREVENTION OF INFLAMMATION
BONE MARROW TRANSPLANTATION
- Inborn defects of hematopoiesis, immunodeficiencies
- Radiation, chemical damage
- Leukaemia, lymphoma
PROBLEM:
- Attack “graft vs. host“ (GvHD)
- Necessity of best possible genetic similarity and strong
immunosuppression
- Ideal – transplantation of pure stem cells
ALLOREACTIVITY IN VITRO
- Mixed lymphocyte reaction (MLR)
Mutual stimulation of allogeneic lymphocytes (mainly
proliferation of TH, also TC): measurement of the rate of
incorporation of radioactive nucleotides
- Use – selection of potential donors
RATE OF TRANSPLANTATE REJECTION
DEPENDS ON:
- Genetic difference between donor and recipient
- Type of tissue
- Activity of recipient immune system
Hyperacute rejection - during minutes to hours
Cause:
antibodies (e.g. xeno-);
complement
Acute rejection– during several days
Cause:
alloreactive T-lymphocytes (TH1, TC)
ALLOREACTIVITY
Genetic difference in MHC (extremely polymorphic): the cells of
the graft carry complexes MHC-peptide completely different
from the recipient cells. Many T-lymphocytes therefore recognize
graft cells as foreign (as if infected).
Genetic differences in v non-MHC: a similar situation; the
number of the “foreign“ complexes is however much lower
XENOREACTIVITY
Similar to alloreactivity; paradoxically even smaller
(partial inter-species incompatibility of adhesive and
signaling molecules).
Big problem – “natural“ xenoantibodies
MOST COMMON TRANSPLANTATIONS
-
Blood transfusion
-
Kidney (> 30 000 per year)
-
Heart (3 000)
-
Liver (5 000)
-
Cornea – mostly no imunological problems;
a “privileged“ site
14.
ANTI-TUMOUR IMMUNITY
ANTI-TUMOUR IMMUNITY
- Tumour-specific antigens (TSA)
- Tumour-associated antigens (TAA)
TSA:
- Complexes of MHC gp with abnormal protein fragments
(mutants; abnormal cleavage). (Chemically induced
tumors)
- Complexes of MHC gp with fragments of oncogenic viruses
(polyoma, SV40, EBV)
- Abnormal forms of glycoproteins
-
Idiotopes of myelomas
TUMOUR ASSOCIATED ANTIGENS (TAA)
ONCOFETAL ANTIGENS:
 -fetoprotein (AFP)
 carcinoembryonal antigen (CEA)
OTHERS
 melanoma antigens (MAGE-1, Melan-A)
 HER-2/neu (growth factor receptor, epithelial cells)
Amplification in breast cancer cells
 EPCAM (epithelial cells; metastases of carcinomas)
 “Differentiation antigens“ in leukaemia (CALLA - CD10)
Diagnostic, partially therapeutic importance
ANTITUMOUR IMMUNE MECHANISMS
- HYPOTHESIS OF “IMMUNOLOGICAL
SURVEILLANCE” (?)
- Inflammation; macrophages (possible stimulation by BCG
injection, Corynebacterium)
- NK (anomalous expression of MHC I)
- Antibodies, TC
MECHANISMS OF TUMOUR RESISTANCE
-
Do not act as APC (absence of costimulatory surface
molecules)
Variability (loss of tumour antigen, immunoselection)
-
Paradoxical stimulatory effect of antibodies
(“enhancement”)
-
Production of factors inactivating generally Tlymphocytes
-
“Blocking factors“ (soluble forms of tumour antigens
shedded from the cell surface)
(privileged tissue!)
TUMOUR IMMUNOTERAPIES BASED ON
ANTIBODIES
-
Monoclonal antibodies, resp. immunotoxins against tumour antigens
Problems:
Damage of normal tissue
Immunoselection of the antigen-loss variants
Accessibility (best after surgery; micrometastases);
EPCAM; HER-2/neu; myelomy
-
Bispecific antibodies (against tumour antigen x against T, NK)
-
Autologous bone marrow transplantation (leukaemia); “purging“ of
leukaemic cells by means of monoclonal antibodies
IMMUNOTHERAPY OF TUMOURS –
CELLULAR MECHANISMS
-
“Non-specific“ stimulation of inflammation (BCG; bladder
carcinomas)
Stimulation of LAK, TIL
-
Improvement of APC-function (transfection of CD80,
cytokines; APC fusion)
-
“Tumour vaccines“ (identification of peptides recognized
by TIL on melanomas and other tumours, optimal
stimulation of TC, TH1)
15.
REGULATION OF IMMUNE
RESPONSES
REGULATION OF IMMUNE RESPONSE
Regulation by antigen
-
Primary regulator (eliciting, finishing of response, affinity
maturation; memory)
-
Antigenic competition (for MHCgp)
Surface density of the MHC-peptide complexes on APC
decisive for TH1 x TH2.
Necessity to achieve a threshold density
-
Agonistic, semi-agonistic, antagonistic peptides
Automatic mechanisms of finishing of the response
(apoptosis of activated T-cells, short life time of most plasma
cells)
REGULATION BY CYTOKINES AND
INTERCELLULAR CONTACT
PROBABLY THE MOST IMPORTANT
MECHANISM OF REGULATION!
APC – T
TH1- M
FDC – B
TH2 – B
TH1 x TH2
(TH – TC)
Development of various leukocyte subpopulations
REGULATION BY ANTIBODIES
- Competition for antigen between
BCR and soluble antibodies
- Crosslinking of BCR and FcR on Bcells by immunocomplexes –
negative signal
- Idiotypic network
NEGATIVE REGULATION
(SUPRESSION)
1) TH1 x TH2 (cytokines)
2) TREG, TS
Possible mechanisms:
- effect on DC (tolerogenic)
- inhibition of TH
- creation of “cytokine environment“ prefering TH2
- anergic cells competing for IL-2
3) Anergization; clonal elimination
(non-professional APC)
ESSENTIAL
IMPORTANCE OF
Treg
MECHANISMS OF Treg
DEVELOPMENT AND SELECTION
IN THYMUS – ALSO Treg!!!
REGULATORY IMPORTANCE OF DC
NEUROENDOCRINE REGULATION
- Neurotransmitters (noradrenaline…) act on leukocytes
- Direct contact of nerve endings and mastocytes
- Many endocrine hormones affect markedly leukocytes
(corticosteroids, growth hormone, thyroxine, endorfins)
- Leukocytes produce hormones (endorfins, ACTH, TSH,
growth hormone etc.)
- Many cytokines act on neuronal system (IL-1, IL-6, LIF,
TNF)
- Clear negative effect of stress on immune system (wound
healing, anti-infection immunity, alergy). Activity of
fagocytes, NK. Mainly the effects of the released
corticosteroids?
IMMUNOLOGIC TOLERANCE
 Immunity x tolerance
 Inability to react to a certain antigen
Physiologically – tolerance to autoantigens
Experimentally – tolerance induction (instead
of immunity) to foreign antigens
 Importance – transplantation; autoimmune
diseases
FACTORS AFFECTING EXPERIMENTAL
TOLEROGENIC RESPONSE
-
State of the immune system (immature; weakened by irradiation,
immunosupresive drugs)
- Properties of antigen (size of the molecule; monomer x polymer,
aggregate)
- Antigen dose (very low and very high doses tend to be tolerogenic)
- Way of application (injection to blood, subcutaneous; adjuvans;
peroral)
- Genetic effects (allelic forms of MHC)
EXPLANATION:
Mainly presentation of antigen (type of APC; density of the MHC-peptide
complexes; TH1 x TH2; activation of TREG)
Immune paralysis, exhaustion (high antigen doses – saturation of binding
sites, activation of all antigen-specific cells at the same time, no memory
cells).
MECHANISMS OF SELF-TOLERANCE
- Elimination of autoreactive clones (negative selection)
- Anergization of immature B-cells
- Ignoring of autoantigens present in small amounts or
isolated from immune system (“invisible“)
- Anergization of T-cells by contact with nonprofessional APC (missing costimulatory signal)
- Activity of various types of TREG, TS
BASIC DOGMA OF THE
ADAPTIVE RESPONSE:
ANTIBODY RESPONSES (B, Th2) – EFFECTIVE
AGAINST EXTRACELLULAR PARASITES
INFLAMMATORY RESPONSES (Th1, Tc) – EFFECTIVE
AGAINST INTRACELLULAR PARASITES
MUTUAL COMPETITION Th1 vs. Th2 (REGULATION BY
POSITIVE FEEDBACK)
WRONG CHOICE OF THE Th1 vs. Th2 RESPONSE
CAN BE FATAL
(LEPROSY…)
Th1 x Th2
(„they don’t like each other …“)
IFNg vs. IL-4
16.
IMMUNOPATOLOGIC
REACTIONS - ALLERGIES
ALERGIES AND OTHER HYPERSENSITIVITIES
Hypersensitivity to harmless antigens; reaction damages the
organism
Type I – Alergy, atopy (IgE)
Type II –
Hemolytic reactions (complement)
against alloantigens (transfusion reaction;
hemolytic disease of the newborn – Rh)
Type III – Caused by immunocomplexes
Type IV – Delayed type (DTH) and contact hypersensitivity
(TH1 reaction)
MECHANISMS OF ALERGIES (TYPE I)
-
Completely analogous to defense IgE reactions against parasites: IgE;
Ig-receptors on mastocytes, basophils and eosinophils
-
Sensitisation; production of IgE; binding to IgE-R
-
After next encounter of allergen - binding to mastocytes coated by IgE –
receptor cross-linking
-
Consequences:

“degranulation” – release of primary mediators (histamine,
enzymes)

stimulation of secondary mediators production (prostanglandins,
leukotrienes – arachidonate derivatives)

local inflammation (1. a 2. phase); swelling of mucosa, secretions,
itching, pain, smooth muscle contraction; 2nd phase – also other
cells participate (typical inflammation)
FACTORS AFFECTING ALLERGIES
- Nature of aergens: unclear why just certain antigens of
pollen, house mites, foods, etc. elicit IgE responses
- Genetic predispositions (polymorphism of MHC genes,
IL-4, IgE-R)
- Environment (exposition to the allergen; climatic
conditions)
- Diet in early childhood (breast feeding?)
- Infections in early childhood (some respiratory viral
infections: bronchial hyperreactivity; absence of intestinal
parasites in childhood? low exposition to antigens in
general? „hygienic hypothesis“)
Incidence of prototypical infectious diseases
and immune disorders 1950 to 2000
N Engl J Med, Vol 347, No. 12, 09/2002
HUGE INCREASE OF ALLERGIES AS „CIVILIZATION
DISEASES“
Epidemiological studies - hygienic hypothesis:
Early childhood on a (primitive) farm (mycobacteria, LPS?)
Intestinal parasites
Breast feeding
Non/pasteurized milk
“Good” intestinal flora
Hepatitis A
Diesel exhaust particles?
Life style in general (DDR vs. FRG, Turkish immigrants,
anthroposophy..)
Allergens that get to blood circulation may cause
systemic anaphylaxis (anaphylactic shock)
- insect venoms
- penicillin (alergens are penicilloylated
proteins)
TREATMENT OF ALLERGIES
- Profylaxis
- Antialergics (blocking of histamine
receptors; corticoids inhibit histamine
synthesis; effects on membrane composition
– inhibition of degranulation)
-
Desensitisation, hyposensitisation (empiric
efforts to enhance competing IgG responses
instead of IgE).
Reliable rational procedures (TH1 x TH2?)
do not exist yet.
TYPE II HYPERSENSITIVITY
Transfusion reaction
(A, B, 0; “isohemagglutinins”)
Minor blood groups
Hemolytic disease of newborn:
85% individuals - RhD+
RhD- mother – immunization by RhD+ foetus (delivery)
Next pregnancy – foetus damage
Prevention: passive immunization anti-RhD before the
first delivery
TYPE III HYPERSENSITIVITY
 Antigen (animal sera, bacterial product, autoantigen) –
elicits antibodies
 Repeated contact with antigen – massive formation of
immunocomplexes
 Binding to Fc-receptors of phagocytes, activation of
ccomplement, deposition in kidney glomerules
 Important component of pathology of pathologies of
some infectious and autoimmune diseases
 “Serum sickness“ – damage of kidney, blood vessels,
joints, skin
 Experimental model: Arthus reaction
TYPE IV HYPERSENSITIVITY (DTH)
- Sensitising antigen natural – e.g. mycobacteria
experimental – protein given in adjuvans
- Following injection subcutaneous, intradermal:
local characteristic reaction after 24-72 hr.
- Mechanism: TH1 – activated macrophages;
inflammation
- Tuberculin reaction
CONTACT HYPERSENSITIVITY
- Low-molecular substances (Ni, CrO42-,
components of cosmetics, varnish, dyes).
Experimental – DNP, DNFB
- Modification of proteins, stimulation of
TH1
- Skin manifestations – essentially DTH
17. IMMUNOPATOLOGIC
AUTOIMMUNE REACTIONS
AUTOIMMUNITY
Immune system reacts to autoantigen.
Causes:
- Molecular mimikry?
- Exposure of hidden autoantigens and cryptic eptitopes
(infection, inflammation)
- Reaction against primary autoantigen intensifies the
inflammation, reaction against further autoantigens
(cryptic epitopes) develops. “Determinant spreading“
Linkages to MHC polymorphism
AUTOIMUNE DISEASES CAUSED BY
AUTOANTIBODIES
Lupus erythematosus autoantibodies to DNA, histones
ribonucleoproteins; DR3
Graves disease autoantibodies to TSH-R; mimick TSH →
overprodukce of thyroxin; DR3
Myasthenia gravis
autoantibodies to AChR; - block effects of ACh; DR3
Hashimoto thyroiditis
autoantibodies to thyroid antigens; decreased production of thyroid
hormones; DR5
Acute rheumatic fever
Antibodies to streptococcal antigens cross-react with surface
antigens of heart muscle.
The only clear case of antigenic mimikry
Disease
Autoantibodies to
Systemic lupus
erythematodes
Nuclear antigens; blood elements
Rheumatoiod arthritis
Fc-fragments of immunoglobulins
("rheumatoid factor")
Dermatopolymyositis
Extractable nuclear antigens Jo-1, PM/Scl
Sjögren’s disease
Extractable nuclear antigens (SS-A, SS-B)
Systemic sclerodermy
Extractable nuclear antigens (Scl-70)
Anti/phospholipide
syndrom
Phospholipids
Some vasculitis
Cytoplasmatic antigens of neutrophils
DISEASES CAUSED BY AUTOREACTIVE T-CELLS
Juvenile diabetes mellitus (IDDM)
TC, TH1 against antigens of -cells of pancreatic of Langerhans
islets
Primary autoantigens – glutamic acid decarboxylase, Hsp60?
Elicited after local inflammation following a viral infection?
DR3, DR4, (protective DR2)
Multiple sclerosis
TH1 against antigens of myelin (presented by microglia);
inflammation; demyelination
DR2
Rheumatoid arthritis
TH1 (secondary??) against joint antigens (collagen, Hsp);
antibodies to immunoglobulins (“rheumatoid factor”); damage of
kidney
DR4
Disease
HLA
Relative risk*
Ankylosing
spondyloarthritis
(Bechterev disease)
B27
87.4
Uveitis
B27
10
Goodpasture syndrom
DR2
15.9
Multiple sclerosis
DR2
4.8
DR3
3.7
Systemic lupus
erythematodes
DR3
5.8
Myasthenia gravis
DR3
2.5
Pemphigus
DR4
14.4
Rheumatoid arthritis
DR4
4.2
Hashimotova thyreoiditis
DR5
3.2
Graves-Basedow disease
THERAPY OF AUTOIMMUNE
DISEASES
Immunosupression (corticosteroids,
antibodies to T-lymphocytes, cyclosporin A)
Ideal – re-establishing of tolerance by
manipulation of the immune system
18.
IMMUNODEFICIENCIES
DEFECTS OF NON-ADAPTIVE (INNATE) PART
OF THE IMMUNE SYSTEM
 Missing of some complement components (Neisseria;
accumulation of immunocomplexes) serious defect – missing of
C1 inhibitor
 Defects of NADPH oxidase (chronic granulomatous disease)
 Chédiak-Higashi syndrome: defect of lysosome-phagosome
fusion
 Leukocyte adhesion deficiency (LAD): defect of leukocyte
integrins (leukocytosis, defective extravasation, no puss
formation)
LAD-2 – defect of L-selectin
DEFECTS ANTIGEN PRESENTATION
 “Bare lymphocyte syndrome”: missing MHC II (defect of a
regulatory transcription factor).
CD4+ T cells are missing
Very rarely – missing MHC I (defect in peptide transport).
Very few CD8+ T
DEFECTS OF B-LYMPHOCYTES AND Ig
PRODUCTION
X-linked agammaglobulinemia (XLA):
almost no B cells and Ig (O.C.Bruton 1952; the first described
inborn immunodeficiency)
Defect in the tyrosine-kinase Btk
X-linked hyper-IgM syndrome
Defect of CD40L (on TH): no affinity maturation, isotype switch.
Only large amounts of IgM against TH independent antigens.
Selective Ig (e.g. IgA) deficits
Surprisingly mild consequences; predisposition to respiratory
infections, allergies, a risk for transfusion (anti-IgA!)
DEFECTS OF T-CELLS
DiGeorge syndrome – developmental defect, anatomic
abnormalities, including missing of thymus.
Nu/nu mice – an important model
Deficiency of adenindeaminase (ADA):
Missing T-cells. Attempts at gene therapy.
Severe combined X-linked immunodeficiency (SCID):
defect in common subunit gc of the receptors for cytokines IL-2, 4, -7, -9, -13, -15.
Similar severe diseases in defects of several other signaling
molecules.
Autosomal recessive SCID – defect of recombination of the Ig
and TCR genes. Missing T and B lymphocytes.
Nu/nu mouse (athymic)
ACQUIRED IMMUNODEFICIENCIES
Temporary or chronic – consequence of some infections,
malnutrition, malignancies, stress (injury trauma), irradiation,
chemicals (high doses of antibiotics, immunosupressants)
AIDS: infected > 40 000 000 people
HIV – retrovirus (lentivirus); tropism for CD4+ T,
monocytes/macrophages
Potentially a number of possible mechanisms of immune system
destruction, e.g.:
 direct and indirect destruction of TH
 destruction of APC including FDC
 affecting TH1 x TH2
 loss of memory T-cells
AIDS - therapy:
 virostatics – (AZT), HAART
 (vaccine development)
 looking for immunotherapy (cytokines; IL-16)
 rare cases of natural resistance (absence of chemokine
receptors)
(successful experimental immunization; HIV-2; chimps)
19.
IMMUNOPROPHYLAXIS AND
IMMUNOTERAPY
IMMUNOPROPHYLAXIS
TERMS:
Active, passive immunization
Vaccines: microorganisms or their components




Atenuated microorganisms
Inactivated microorganisms
“Subunit“ vaccines
Toxoids
Prophylactic x therapeutic vaccination
Danger of infection or anaphylaxis
Adjuvants (incomplete, complete Freund adjuvans; alum)
The way of administration is important – immunogenic x tolerogenic:
- monomeric x polymeric, aggregated antigen
- parenteral x subcutaneous x peroral
PASSIVE IMMUNIZATION
Natural – maternal antibodies (transplacental, milk)
Prophylactic, therapeutic:
 animal antisera to toxins (danger of anaphylaxis after
repeated administration)
 human IgG (hepatitis, rabies, tetanus; Ig-deficiency);
intramuscular, resp. highly purified intravenous
 Anti-Rh (prevention of production of own anti-Rh)
ACTIVE IMMUNIZATION
E. Jenner: Vaccinia – against pox (variola)
(ERADICATION 1970!)
Atenuated live vaccines (most efficient)
measles, mumps, rubella, polio (peroral), yellow fever,
tuberculosis (BCG – only in risk groups, total - 2,5 billion)
Subunit vaccines (in adjuvans)
pertussis (toxoid), hepatitis B (recombinant surface antigen),
hemophilus, meningococcus (polysaccharide antigens)
Killed bacteria, inactivated viruses
pertussis, tetanus, cholera, plague, typhoid, influenza, rabies
(therapeutic immunization - “outruns“ slow infection!)
NEW TYPES OF VACCINES (UNDER
DEVELOPMENT)
 Recombinant Vaccinia virus or other vectors
(bird poxviruses, adenoviruses, genetically modified
Salmonella, BCG and other bacteria)
 Futuristic approach – expression in edible plants
 “Genetic vacination“ directly by expression plasmid
(injection into muscle, “gene gun“)
 Better adjuvantsand immunostimulatory substances
Experimentally – carrier KLH, immunostimulators
(cytokines, LPS); severe side effects
MARKED SUCCESS – THERAPEUTIC
MONOCLONAL ANTIBODIES:
Discovery 1976, Nobel prize 1984.
Not patented…
>15 years technical difficulties in therapeutic uses
Last cca 10 years – huge progress (humanized mAb), most
dynamic field of pharmaceutic industry, sales over 20 billion
USD per year…
Cca 30 approved by FDA, other cca 100 under testing
Unconjugated mAbs
Nature Biotechnology 23, 1147 - 1157 (2005)
Trastuzumab
(Herceptin)
Humanized
Rituximab
(Rituxan)
Murine-human Human
CD20
chimeric
IgG1
Lymphoma
Cetuximab
(Erbitux)
Murine-human Human EGF
chimeric
IgG1
receptor
Colorectal cancer 2004
Bevacizumab
(Avastin)
Murine-human Human
VEGF
chimeric
IgG1
Colorectal, lung
cancers
2004
Chronic
lymphocytic
leukemia
2001
Alemtuzumab
(Campath-1H)
Humanized
Human
HER2/neu Breast cancer
IgG1
Human
CD52
IgG1
1998
1997
Immunoconjugates
Ibritumomab tiuxetan
(Zevalin) together
Murine
with rituximab
Tositumomab and 131I
Murine
tositumomab (Bexxar)
Gemtuzumab
(Myelotarg)
Human (drug
derived from
streptomycete)
90
Y-radiolabeled
CD20
murine IgG1
Lymphoma 2002
131
I-radioabeled
CD20
murine IgG2a
Human IgG4
conjugated to
calicheamicin
CD33
Lymphoma 2003
Acute
myelogenous 2000
leukemia
HOPEFULLY IN FUTURE:
- BETTER VACCINES (HIV, WEAK AND TUMOR
ANTIGENS?)
- BETTER IMMUNOSUPPRESSION (AUTOIMMUNE
DISEASES, ALLERGIES, TRANSPLANTATION)
- EFFECTIVE IMMUNOTHERAPIES OF TUMOURS (A
WEAK SPOT OF IMMUNITY…)