Transcript a few milestones in transplantation

TRANSPLANTATION
IMMUNOLOGY
ARPAD LANYI PhD
[email protected]
Further reading: Peter Parham, The Immune System 4th Ed. Chapter 15
Abul K. Abbas, Cellular and Molecular Immunology 8th Ed. Chapter 17
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A FEW MILESTONES IN TRANSPLANTATION
First Human-To-Human Blood Transfusion
James Blundell, 1818
Photo: Blundell's Gravitator Source: NIH/ Pennsylvania State University Libraries
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A FEW MILESTONES IN TRANSPLANTATION
18th century: succesful transplant experiments is animals (skin grafts)
First succesful fresh skin allograft 1869 Jacques Louis Reverdin
First Successful Human-To-Human Bone Transplant 1878
This operation, which used bone from a cadaver, remained unusual because
there was no way to process and preserve human tissues.
Thyroid transplantation 1883 Theodor Kocher
Thyroid transplantation became the model for a whole new therapeutic
strategy: organ transplantation. After the example of the thyroid, other
organs were transplanted in the decades around 1900.
First Attempts At Bone Marrow Transplant 1896
First attempts to use bone marrow as treatment for leukemia; patients
receive the marrow orally after meals, but it has no effect. In the next few
years, intravenous injections of bone marrow to treat aplastic anemia have
some success.
Discovery of ABO blood groups 1902 Karl Landsteiner
First human xenotransplant 1906
A French surgeon inserts slices of rabbit kidney into a child suffering from
kidney failure. The immediate results are good, but the child dies after two
weeks. Four years later, a monkey kidney is transplanted into a young girl
suffering from mercury poisoning; it produces a small amount of urine, but
the girl lives for only five days.
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A FEW MILESTONES IN TRANSPLANTATION
Discovery of MHC 1940’ George Snell
Human HLA: 1958 Jean Dausset
First successful human kidney transplant (syngraft) 1954
Joseph E. Murray
First Successful Human Heart Transplant 1967
"It's going to work!" Dr. Christiaan Barnard shouts as the heart of Denise Darvall,
a 23-year-old woman who died in an automobile accident, begins to beat in the
chest of 54-year old Louis Washkansky. The transplant was performed at Groote
Schuur Hospital in Cape Town, South Africa. The heart functioned until
Washkansky died of pneumonia eighteen days later because of his suppressed
immune system.
First Successful Bone Marrow Transplant 1973
Doctors at the Memorial Sloan-Kettering Cancer
Center in New York City perform the first successful
bone marrow transplant from an unrelated donor. They
transplant marrow from a person in Denmark into a
five-year-old with severe combined immunodeficiency
disease known as bubble boy syndrome. A few
successful previous bone marrow transplants had all
involved related donors.
PEOPLE IN THE US LIVING WITH FUNCTIONING ORGAN GRAFTS
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The success of transplantation and survival
of the donor tissue
depends majorly on histocompatibility
TYPES OF TRANSPLANTATION
AUTOLOGOUS
autograft
SYNGENEIC
syngraft
TOLERANCE
ALLOGENEIC
allograft
ALLOREACTION
GRAFTS WITH MATCHING MHC ARE TOLERATED
WHILE ALLOGENEIC GRAFTS ARE REJECTED
ALLORECOGNITION
DIRECT AND INDIRECT
ALLOANTIGEN RECOGNITION
MOLECULAR BASIS OF DIRECT
RECOGNITION OF
ALLOGENEIC MHC MOLECULES
The frequency of T-cells that can directly recognize
allogeneic MHC molecules is extremely high (1-10%)
• Every APC expresses thousands of copies of
the allogeneic MHC molecules: strong stimuli
• Many different donor-derived peptides: many
clones of recipient T-cells
• Memory T-cells - cross-reaction
DIRECT AND INDIRECT ALLOANTIGEN
RECOGNITION
It is essentially the same as the
recognition of any foreign (e.g.,
microbial) protein antigen
ACTIVATION OF ALLOREACTIVE
T-CELLS
Antibodies
against
graft
antigens
(most
frequently HLA) also contribute to rejection.
Antibody production follows the same sequence of
events as any helper T-cell-dependent antibody
response (indirect recognition).
TRANSPLANT REJECTION
BLOOD TRANSFUSION IS THE MOST COMMON FORM
OF TISSUE TRANSPLANTATION
Incompatibility of blood group antigens causes type II hypersensitivity reactions
Incompatibility is tested by the cross-match test.
The patient’s serum is tested against the red cells of the potential donors.
The patient’s red cells are NOT tested against the serum of the donor!!!
Organ transplantation requires compatibility of the main blood group antigens
HYPERACUTE TRANSPLANT REJECTION
IS AN ANTIBODY-MEDIATED TYPE II HYPERSENSITIVITY REACTION
• The most dramatic form of tissue incompatibility, begins within minutes to hours
• BLOOD GROUP ANTIGENS are expressed by endothelial cells of blood vessels (solid
vascularized organs)
• ANTIBODIES – COMPLEMENT FIXATION – NEUTROPHIL, PLATELET ACTIVATION –
INTRAVASCULAR COAGULATION - IRREVERSIBLE ISCHEMIC NECROSIS
• Cannot be reversed, should be avoided!!!!!
• Today, hyperacute rejection by anti-ABO antibodies is extremely rare
BUT
• HLA I is expressed on vascular endothelium cells, preexisting antibodies (IgG) against HLA
class I variants can also cause hyperacute rejection!!
Where do anti-HLA antibodies come from?
THE SOURCES OF ANTI-HLA ANTIBODIES
Pregnancy – during childbirth
With successive pregnancies, increasing levels of anti-HLA
antibodies can develop
Blood transfusions (platelets, leukocytes) - HLA type is not
assessed, the matching being restricted to just the ABO and
Rhesus D types
Previous organ transplant
Cross-match!!!
CROSSMATCH TESTING
Complement-dependent
cytotoxicity
Flow cytometry
Panel reactive antibody
(PRA)
Beads:
Bb
DOI: 10.1111/j.1440-1797.2010.01414.x
ACUTE TRANSPLANT REJECTION
IS A T-CELL-MEDIATED TYPE IV HYPERSENSITIVITY
REACTION
The rejected graft is swollen and
has deep-red areas of
hemorrhage and gray areas of
necrotic tissue.
ACUTE TRANSPLANT REJECTION
IS A T-CELL-MEDIATED TYPE IV HYPERSENSITIVITY
REACTION
Lymphocytes around an
arteriole (A)
Lymphocytes surrounding the
renal tubules (T)
Staining of T
lymphocytes with antiCD3 (brown) in the same
section
CHRONIC TRANSPLANT REJECTION
IS A TYPE III HYPERSENSITIVITY REACTION
Thickening of the vessel walls and narrowing of their lumens
E: endothel
G: granulocyte
T: alloreactive T
M: macrophage
EL: elastic lamina
SMC: smooth muscle cell
Chronic rejection in a kidney
allograft with graft
arteriosclerosis
HLA MATCHING IMPROVES THE SURVIVAL OF TRANSPLANTED
ORGANS (for example kidneys)
Blue
Orange
Red
Dark blue
Green
Black
Brown
HLA-A, B, C and DR are the most important to match
HLA TYPING
MIXED LYMPHOCYTE REACTION
The response of alloreactive T-cells to foreign MHC
molecules can be analyzed in vitro
DNA-BASED TYPING METHODS
• PCR-SSOPH: Sequence-specific oligonucleotide probe hybridization
• Intermediate resolution, High volume, relatively low cost
• Sreening test to identify potential donors or individuals who may
later require higher resolution testing
• SSP-PCR: Sequence-specific PCR (allele-specific primers)
• Rapid (3-4 hours)
• Typing of deceased organ donors (speed is important)
• SBT: Sequence-based typing
• Polymorphic regions are amplified by PCR and then sequenced
• The highest resolution HLA typing
EVEN COMPLETE MATCHING AT THE MHC DOES NOT ENSURE
GRAFT SURVIVAL
MINOR HISTOCOMPATIBILTY ANTIGENS
Peptides derived from polymorphic cellular proteins bound to MHC class I molecules
The response to minor H antigens is in many ways analogous to that of viral infection
MINOR HISTOCOMPATIBILITY
ANTIGENS
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IMMUNOSUPPRESSIVE
THERAPY
DEPLETING ANTIBODIES
Antibodies that broadly react with white blood cells are given to patients
before and after transplantation
to deplete these cells and generally weaken the immune system
• Rabbit antithymocyte globulin (rATG)
• Polyclonal mixture of high-affinity antibodies
• Binds to T-, B-, NK, dendritic and endothelial cells
• Fixes human complement well, delivers the cells to be killed
by phagocytes
• Alemtuzumab: anti-CD52
• CD52-specific humanized rat monoclonal IgG
• CD52 is expressed on almost all lymphocytes, monocytes
and macrophages
• Complement fixation, phagocytosis
• Alemtuzumab induces a profound, long-lasting lymphopenia
CORTICOSTEROIDS ARE EFFECTIVE
IMMUNOSUPPRESSIVE DRUGS
EFFECTS OF CORTICOSTEROIDS ON THE IMMUNE SYSTEM
• Used to treat patients before the
transplantation and during episodes of
rejection
• Many
adverse
side-effects:
fluid
retention, weight gain, diabetes, loss of
bone mineral, thinning of the skin
• Prolonged use is avoided wherever possible
• Need novel, milder drugs
T-CELL ACTIVATION CAN BE TARGETED
BY IMMUNOSUPPRESSIVE DRUGS
Calcineurin inhibitors: cyclosporin, tacrolymus
Side effects: Neurotoxicity, Nephrotoxicity, Diabetes
INFLUENCE OF CYCLOSPORINE ON GRAFT SURVIVAL
INHIBITION OF T-CELL CO-STIMULATION BY BELATACEPT,
A SOLUBLE FORM OF CTLA-4
Belatacept works as well as the best of the older, established drugs
Better than them in preserving kidney function
BUT!!! Belatacept is associated with increased incidence of episodes of acute rejection
BLOCKING CYTOKINE SIGNALING
CAN PREVENT ALLOREACTIVE
T-CELL ACTIVATION
Chimeric basiliximab, humanized daclizumab:
monoclonal IgG1 antibodies specific for CD25
Specific for activated T-cells:
no wide-ranging effects and immunosuppression
associated with many other drugs
mTOR INHIBITOR: RAPAMYCIN (SIROLIMUS)
(Streptomyces hygroscopicus)
doi:10.1038/nri2546
• Binds to FKBP12, but does not interfere with calcineurin
• More toxic than either cyclosporin A or tacrolimus but is a useful
component of combination therapy
• Does not inhibit the survival and functions of regulatory T-cells
CYTOTOXIC DRUGS TARGET THE REPLICATION AND
PROLIFERATION OF ALLOANTIGEN-ACTIVATED T-CELLS
Cytotoxic drugs are administered only after transplantation
Azathioprine: kidney transplantation
• Prodrug, first converted in vivo to 6-mercaptopurine and then to 6thioinosinic acid
• The latter inhibits the production of inosinic acid, an intermediate in
the biosynthesis of adenine and guanine nucleotides
• No selectivity, collateral damage to those tissues that are always
engaged in cell division: bone marrow, intestinal epithelium, hair
follicles: anemia, leukopenia, thrombocytopenia, intestinal damage,
loss of hair
Mycophenolate mofetil:
• Penicillium stoloniferum
• Similar effects to those of azathioprine
• Metabolized in the liver to mycophenolic acid
• Prevents cell division by inhibiting inosine monophosphate
dehydrogenase, an enzyme necessary for guanine synthesis
CYTOTOXIC DRUGS TARGET THE REPLICATION AND
PROLIFERATION OF ALLOANTIGEN-ACTIVATED T-CELLS
Cytotoxic drugs are administered only after transplantation
Cyclophosphamide:
• Originally developed as a chemical weapon (World War I.)
• A pro-drug that is metabolized to phosphoramide mustard, a compound
that alkylates and cross-links DNA molecules
• Specifically damages the bladder, sometimes causing cancer or
hemorrhagic cystitis.
• Unlike azathioprine, cyclophosphamide is not particularly toxic to
the liver, useful alternative for patients with liver damage
• Cyclophosphamide is most effective when used in short courses of
treatment
Methotrexate:
• Prevents DNA replication by inhibiting dihydrofolate reductase, an
enzyme essential for the cellular synthesis of thymidine.
SUMMARY OF IMMUNOSUPPRESSIVE DRUGS ACTING AT
DIFFERENT STAGES IN THE ACTIVATION OF ALLOREACTIVE TCELLS
The need for HLA matching and immunosuppressive
therapy varies with the organ transplanted
Corneal transplants: tolerogenic immunological environment
90% success in the absence of HLA matching or immunosuppressive
therapy
Liver: tolerogenic immunological environment, low HLA1 expression,
HLA type is not assessed before transplantation
At the other end of the spectrum from eye and liver
is the bone marrow
HEMATOPOIETIC STEM CELL
TRANSPLANTATION
HEMATOPOIETIC STEM CELL TRANSPLANTATION (HSCT)
• Myeloablative therapy: combination of cytotoxic drugs and
irradiation
• Engraftment: pluripotent stem cells colonize the bones
• When the immune system has been fully reconstituted (can take a
year or more), the patient is a chimera (has an immune system
which is genetically different)
•
•
•
•
•
HSCs are now obtainable from the blood
G-CSF, GM-CSF: stem cells are mobilized from the bone marrow
Leukapheresis
Isolation: CD34
Between a quarter and half a billion CD34-positive cells are needed
to ensure prompt engraftment
MORE SHARED HLA ALLOTYPES,
MORE ROBUST T-CELL RESPONSE
THE SUCCESS OF HSCT CORRELATES WITH THE EXTENT
OF THE HLA MATCH
GRAFT-VERSUS-HOST DISEASE: ALLOREACTIVE DONOR TCELLS IN THE GRAFT ATTACK THE RECIPIENT’S TISSUES
The conditioning regimen creates cytokine storm
A systemic type IV hypersensitivity reaction that can
prove fatal
GRAFT-VERSUS-HOST DISEASE: ALLOREACTIVE DONOR TCELLS IN THE GRAFT ATTACK THE RECIPIENT’S TISSUES
Prevention: T-cell depletion
Treatment: Methotrexate in
combination with cyclosporin A
Markedly
reduced
GVHD:
higher incidence of graft
failure
A systemic type IV hypersensitivity reaction that can
prove fatal
THE PROBABILITY OF GVHD CORRELATES STRONGLY WITH THE
EXTENT OF HLA MISMATCH
Minor histocompatibility antigens trigger
alloreactive T-cells in recipients of HLA-identical transplants (red)
TRANSPLANT REJECTION VS GVHD
UMBILICAL CORD BLOOD AS THE SOURCE OF
HEMATOPOIETIC STEM CELLS
• Umbilical cord blood has the combined benefits of being rich
in stem cells and having fewer alloreactive T-cells
• There is less GVHD, and a greater HLA disparity can be
tolerated
• Engraftment is slower
• Limited volume: combined stem cells from two unrelated
samples of cord blood
• The patient’s reconstituting hematopoietic system becomes a
chimera but in time the cells from one donor overwhelm the
cells of the second
• First use: 1988; child with Fanconi’s anemia
• More than 25,000 cord blood transplants have been performed
GENETIC DISEASES FOR
WHICH HSCT IS A THERAPY
HSCT is a therapy for many
genetically determined
immunodeficiencies, such as
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SCID
HSCT IN TUMOR THERAPY
Autologous HSCT
• A sample of the patient’s bone marrow is taken before the
remainder is ablated
• The hematopoietic stem cells in are purified away from any
tumor cells and are then given back to the patient
• Perfectly histocompatibility: no GVHD, no immunosuppressive
drugs
• Limitation: the rate of relapse is significantly higher for
autologous transplants than for allogeneic transplants
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GRAFT-VERSUS-LEUKEMIA (GVL) EFFECT
Alloreactive T-cells in the graft help rid the patient of residual leukemia cells
• Promotion of GVL reaction, less emphasis on tumor elimination by
chemotherapy and irradiation
• Less severe conditioning regimens: hematopoietic system is
damaged but not destroyed, quicker recovery
• One approach: transfusions of donor T- cells at a time after
transplantation when the inflammation caused by the conditioning
regimen has subsided and the likelihood of GVHD is diminished
NK CELL-MEDIATED GVL EFFECT
Reconstitution of NK cells occurs more rapidly than that of T-cells
Alloreactive NK cells can emerge
NK CELL-MEDIATED GVL EFFECT
Myelogenous leukemia: a haploidentical transplant is the best choice
NK CELL-MEDIATED GVL EFFECT
NK-cell alloreactions occur when the recipient’s HLA class I
allotypes provide ligands for fewer types of inhibitory KIR than
the donor’s HLA class I allotypes
NK CELL-MEDIATED GVL EFFECT
Potential donors are mothers, fathers, and 50% of siblings
METHODS TO INDUCE DONOR-SPECIFIC TOLERANCE
Hematopoietic chimerism
• Dizygotic twins who have had a common blood circulation during
gestation are tolerant of each other’s tissues.
• Combining solid organ transplantation with some mild form of
hematopoietic cell transplant from the same donor could
induce a more robust and stable tolerance and eliminate the
necessity for long-term immunosuppression.
• Promising results: renal/bone marrow allograft
• Family members differing by one HLA haplotype
• Non-myeloablative treatment: cyclophosphamide, cyclosporin,
anti-CD2 antibody, thymic irradiation
• Immunosuppressive therapy: 9–14 months
• Survival: up to 10 years
Transfer of regulatory T-cells
• Attempts to generate donor-specific regulatory T-cells in culture
and to transfer these into graft recipients are ongoing.
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