Transcript External regulation of immune response

External regulation of
immune response
J. Ochotná
Causal treatment
a) Stem cell transplantation
 for serious congenital disorders of the immune system (some
lymphoproliferative and myeloproliferative disorders)
 complications: infectious complications
Graft-versus-host
 obtaining stem cells - collection from shovel hip bone
- from umbilical cord blood
- from peripheral blood after stimulation
with GM-CSF
b) Gene therapy
 with a suitable expression vector is introduced functional
gene (to replace dysfunctional gen) into the lymphocytes
or stem cells
 used as a treatment for some cases of SCID
Substitution treatment
 autologous stem cell transplantation following
chemotherapy and radiotherapy
 treatment with intravenous immunoglobulin (derived from
plasma of blood donors)
 substitution of C1 inhibitor for hereditary angioedema
 substitution of erythropoietin in patients with chronic renal
failure
 substitution of G-CSF in agranulocytosis
Immunomodulation
= medical procedure to adjust the disrupted immune function
Non-specific immunosuppressive therapy
 nonspecific = affects not only autoreactive and aloreactive
lymphocytes, but also other components of
immunity
(risk of reduction antiinfectious and antitumor immunity)
 used for treatment of autoimmune diseases, severe allergic
conditions and for organ transplantation
Non-specific immunosuppressive therapy
 corticosteroids - anti-inflammatory, immunosuppressive
effects
- blocking the activity of transcription
factors (AP-1, NFkB)
- suppress the expression of genes (IL-2,
IL-1, phospholipase A, MHC gp II,
adhesion molecules)
- inhibition of histamine release from basophils
- higher concentrations induce apoptosis
of lymfocytes
 immunosuppressants affecting the metabolism of DNA
- cyclophosphamide
- methotrexate
 immunosuppressant selectively inhibiting T lymphocytes
- immunosuppressive ATB: cyclosporine A, tacrolimus,
rapamycin (suppressing the expression of IL-2 and
IL-2R in activated T lymphocytes)
- monoclonal antibody anti-CD3 (Immunosuppression
after transplantation, treatment of rejection crises)
 immunoglobulins in the immunosuppressive indication
- Polyspecific intravenous immunoglobulins
(Inhibition of B lymphocytes, antiidiotype activity,
inhibition of cytokines, neutralization of toxins,
inhibition of complement activation ...)
Anti-inflammatory and antiallergic treatment
 nonsteroidal anti-inflammatory drugs
 antihistamines - blocking H1 receptor
- reduce the expression of adhesion
molecules
- reduce the secretion of histamine ...
 inhibitors of inflammatory cytokine
- receptor antagonist for IL-1
- monoclonal antibodies against TNF
- thalidomide (TNF inhibitor)
 enzyme therapy - in the enzyme mixture has a major
effect trypsin and bromelain
- anti-inflammatory
and immunomodulatory effects
Non-specific immunostimulant therapy
 synthetic immunomodulators
 Methisoprinol (Isoprinosine) - used in viral infections with more
severe or relapsing course
 bacterial extracts and lysates
 Broncho-Vaxom - prevention of recurrent respiratory tract infections
 Ribomunyl
 products of the immune system
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IL-2 - renal adenocarcinoma
IFNa, IFNb - viral hepatitis, some leukemia
Erythropoietin – renal failure
G-CSF, GM-CSF – neutropenia
Transfer factor (blood donors leukocytes undergoing dialysis)
Thymus hormones
Antigen-specific immunomodulatory therapy
 specific immunomodulation = induce an immune
response or tolerance against a specific antigen
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a) active immunization
= use of antigen to induce an immune response that can
later protect against a pathogen bearing the antigen
(or similar antigen)
immunization vaccines are made from inactivated or
attenuated microorganisms or their antigens
(polysaccharide capsule, toxins)
creates long-term immunity
activate cellular and antibody immunity
administration of antigen injectable, oral
prophylaxis
risk of causing infection or anaphylactic reactions
b) passive immunization
 natural - transfer of maternal antibodies in fetal blood
 therapeutically - the use of animal antibodies against
various toxins (snake toxins, tetanus
toxin, botulinum toxin)
 prophylaxis - the human immunoglobulin from
immunized individuals (hepatitis A,
rabies, tetanus)
- Anti-RhD antibodies - preventing
maternal immunization with RhD+ fetus
 provides a temporary (3 weeks) specific humoral
immunity
 the risk of induction anaphylactic reactions
c) specific immunosuppression
= induction of tolerance against a specific antigen
 ongoing clinical studies
 induction of tolerance by oral administration of antigen
(treatment of certain autoimmune diseases)
 allergen immunotherapy (pollen, insect poisons)
d) vaccination against cancer
 s a promising approach appears to immunization
dendritic cells
Defence against
extracellular pathogens
Defence against extracellular pathogens
 bacteria (gram-negative, gram-positive cocci, bacilli),
unicellular parasites
 for their elimination is necessary opsonization (C3b, lectins,
antibodies ...)
 neutrophilic granulocytes are chemotactic attracting to the site
of the infection (C5a, C3a and chemotactic products of
bacteria)
 absorbed bacteria are destroyed by the microbicidal systems
(products of NADP-H oxidase, hydrolytic enzymes and
bactericidal substances in lysosomes)
 phagocytes production of proinflammatory cytokines
(IL-1, IL-6, TNF) that induce an increase in temperature,
metabolic response of the organism and synthesis of
acute phase proteins
 in later stages of infection are stimulated antigen-specific
mechanisms
 plasma cells initially produce IgM isotype after isotype
switching produce IgG1 and IgA (opsonization)
 sIgA protect against intestinal and respiratory infections
by bacteria
 bacteria with a polysaccharide capsule may cause
T-independent IgM antibody production (after the
establishment to the bacteria activate the classical
complement path)
 after infection persist IgG, IgA (protective effect) and
memory T and B lymphocytes
 in the defense against bacterial toxins apply neutralizing
antibodies (Clostridium tetani and botulinum ...)
 "indirect toxins - bacterial Lipopolysaccharide (LPS)
stimulates big number of monocytes to release TNF,
which can cause septic shock
 extracellular bacterial infections are especially at risk
individuals with disorders in the function of phagocytes,
complement and antibody production
Defence against
intracellular pathogens
Defense against intracellular pathogens
 bacteria, fungi and unicellular parasites
 intracellular parasitism is given by the ability
of microorganisms to escape microbicidal mechanisms
of phagocytes
 macrophages, which absorbed them, produce IL-12 → TH1
differentiation, production of IFNg and membrane TNF →
activation of macrophages and induction of iNOS
 plasma cells under the influence of IFNg produce IgG2,
immune complexes containing IgG2 bind to Fc receptors on
macrophages and thus stimulate them
 in the defense against intracelular parasites, which
escape from phagolysosomes apply TC lymphocytes
 intracellular microorganisms infections are at risk
individuals with certain disorders of phagocytes and
defects of T lymphocytes
Anti-viral defence
Anti-viral defence
 interferons - in infected cells is induced production of
IFNa and IFNb (prevents viral replication and in
uninfected cells cause the anti-virus status); IFNg
stimulates the conversion to activated macrophages
(iNOS)
 NK cells - ADCC (Antibody-dependent cell-mediated
cytotoxicity) = cytotoxic reaction depends on the
antibodies; the NK-lymphocyte recognizes cell opsonized
with IgG by stimulation Fc receptor CD16 and then
activate cytotoxic mechanisms (degranulation)
 infected macrophages produce IL-12 (a strong activator
of NK cells)
 in the defense against cytopathic viruses mostly applied
antibodies:
 sIgA inhibit mucosal adhesion of viruses (defense
against respiratory viruses and enteroviruses)
 neutralizing IgG and IgM antibodies activate the
classical way of complement, which is capable of
some viruses lysis
 IgA and IgG derived in viral infection have a
preventive effect in secondary infection
 effector TC lymphocytes destroy infected cells in direct
contact (granzym/perforin; FasL) and by produced
cytokines (lymfotoxin)
 some viruses after infection integrate into the host
genome, where persist for years (varicella zoster, EBV,
papillomavirus)
 by these infections are at risk individuals with T lymphocyte
immunodeficiency and with combined immune disorders
 increased susceptibility to herpes infections in individuals
with dysfunction of NK cells
Defense against
multicelular parasites
Defense against multicelular parasites
 contact of mast cells, basophils and eosinophils with
parasite antigens
 TH2 stimulation under the influence of IL-4 (mast cells
and other APC stimulated by parasite)
 TH2 stimulate B cells with BCR-specific parasite antigens
 isotype switching under the influence of IL-4 to IgE
 IgE bind to FceRI on mast cells and basophils („antigenspecific receptors“)
 establish of multivalent antigen (multicellular parasite)
using the IgE to highafinity Fc receptor for IgE (FceRI)
aggregation of several molecules FceRI
 initiate mast cell degranulation (cytoplasmic granules
mergers with the surface membrane and release their
contents)
 activation of arachidonic acid metabolism (leukotriene
C4, prostaglandin PGD2) - amplification of inflammatory
responses
 start of production of cytokines (TNF, TGFb, IL-4, 5,6 ...)
by mast
 in later stages are activated TH1 and are produced
antibodies of other classes
 eosinophils fagocyte complexes of parasitic particles with
IgE via their receptors for IgE
 eosinophils use against parasites extracellular
bactericidal substances released from granules
(eosinophil cationic protein, protease)
Activation of mast cell
Tumour immunology
Malignant transformation
 failure of regulation of cell division and regulation of
"social" behavior of the cells
 the uncontrollable proliferation, dissemination to other
tissues
 mutations in protoonkogenes and antionkogenes
Tumor cells
 unlimited growth (loss of contact inhibition)
 growth without stimulating growth factors
 immortality (cancer cells have not a limited number
of generations as normal cells)
 often altered number of chromosomes as frequent
chromosomal alteration
 TSA ...
Tumor antigens
a) Antigens specific for tumors (TSA)
 complexes of MHCgp I with abnormal fragments of
cellular proteins - chemically induced tumors
- leukemia with chromosomal translocation
 complexes of MHC gp with fragments of proteins of
oncogenic viruses - tumors caused by viruses (EBV, SV40,
polyomavirus)
 abnormal forms of glycoproteins - sialylation of surface
proteins of tumor cells
 idiotypes of myeloma and lymphoma - clonotyping TCR
and BCR
b) Antigens associated with tumors (TAA)
 present also on normal cells
 differences in quantity, time and local expression
 auxiliary diagnostic markers
1) onkofetal antigens
 on normal embryonic cells and some tumor cells
 a-fetoprotein (AFP) - hepatom
 canceroembryonal antigen (CEA) - colon cancer
2) melanoma antigens
 MAGE-1, Melan-A
3) antigen HER2/neu
 receptor for epithelial growth factor
 mammary carcinoma
4) EPCAM
 epithelial adhesion molecule
 metastases
5) differentiation antigens of leukemic cells
 present on normal cells of leukocytes linage
 CALLA -acute lymphoblastic leukemia (CD10 pre-B cells)
Anti-tumor immune mechanisms
Immune control
 tumor cells normally arise in tissues
and are eliminated by T lymphocytes
 probably wrong hypothesis
Defensive immune response
 tumor cells are weakly immunogenic
 occurs when tumor antigens are presented to T lymphocytes
by dendritic cells activated in the inflammatory environment
 if tumor cells are detected, in defense may be involved nonspecific mechanisms (neutrophilic granulocytes,
macrophages, NK cells) and antigen-specific mechanisms
(complement activating antibodies or ADCC, TH1 and TC)
 cancer-associated antigens are processed by APC and
recognized by T lymphocytes in complex with HLA I.
and II. class with providing costimulus signals
 predominance of TH1 (IFN g, TNFa)
 specific cell-mediated cytotoxic reactivity – TC
 activation of TH2 → support B lymphocytes→ tumor
specific antibodies (involved in the ADCC)
 tumor cells are destroyed by cytotoxic NK cells (ADCC)
Mechanisms of tumor resistance to the
immune system
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 high variability of tumor cells
 low expression of tumor antigens
 sialylation
 tumor cells signals do not provide costimulus → T
lymphocyte anergy
 some anticancer substances have a stimulating effect
 production of factors inactivating T lymphocytes
 expression of FasL → T lymphocyte apoptosis
 inhibition of the function or durability dendritic cells (NO,
IL-10, TGF-b)