Transplantation immunology

Transplantation Immunology
Thansinee Saetae, MD.
Pediatric Allergy and Immunology Unit
King Chulalongkorn Memorial Hospital

Outline
• General principle of transplantation immunology
• Adaptive immune responses to allografts
• Patterns and mechanisms of allograft rejection
• Prevention and treatment of allograft rejection
• Hematopoietic stem cell transplantation (HSCT)
• Graft-Versus-Host diseases
• Immunodeficiency after hematopoietic stem cell
transplantation
• HSCT for the treatment of primary immunodeficiencies
• Severe Combined Immunodeficiencies
• Others PID

General Principles of
Transplantation Immunology

General principles of
transplantation immunology
• Transplantation of cells or tissues from one
individual to a genetically non-identical individual
invariably leads to rejection of the transplant due
to an adaptive immune response.
• Autologous graft: the same individual
• Syngeneic graft: genetically identical individuals
• Allogeneic graft or allograft: two genetically
different individuals of the same species
• Xenogeneic graft or xenograft: between individuals
of different species.
Abbas AK., Litchman AH and Pillai S. Cellular and Molecular Immunology 9th edition, 2018

• Living donors can donate
• one kidney, a lobe of a lung, and parts of liver, pancreas,
or intestine
• Deceased donors, called cadaveric donors, are
sources of any transplantable organ and the only
source of organs that could not be removed from a
living donor
• heart
Donors

• Genetically relate to the recipient
• siblings, parents, aunts, uncles, cousins, nieces, and
nephews
• Related donors will share more alleles of
polymorphic genes, including MHC genes, than
unrelated donors.
• reduce the incidence and severity of rejection episodes
• There is 25% chance that two siblings will have identical
MHC genes
• The chance of an unrelated donor and recipient having
identical MHC genes is extremely low.
Recipients

Adaptive Immune Responses
to Allograts

ADAPTIVEIMMUNERESPONSESTOALLOGRAFTS 361
Skin graft
Donor
(Strain A)
Recipient
(Strain B)
Donor
(Strain A)
Recipient
(Strain B)
Donor
(Strain A)
Recipient
(Strain B)
Graft rejection
Day 3-7?
Graft rejection
Day 10-14??
Yes
YesNo
Recipient (Strain B sensitized
by previous graft from strain
A donor)
First set rejection
Second set rejection Second set rejection
Yes
Recipient (Strain B injected
with lymphocytes from another
strain B animal that rejected
a strain A graft)
FIGURE 17-2 First - and second-set allograf t reject ion. Results of the experiments shown indicate that graft rejection displays the
Graft rejection displays the features of adaptive immune
responses, namely, memory and mediation by lymphocytes.

Adaptive immune responses
to allografts
• The antigens that stimulate adaptive immune
responses against allografts are histocompatibility
proteins, encoded by polymorphic genes that differ
among individuals.
• Major histocompatibility complex (MHC) molecules:
• The molecules responsible for strong (rapid) rejection
reactions.
• Human MHC molecules are called human leukocyte antigens
(HLA)
• Minor histocompatibility antigens:
• Polymorphic antigens other than MHC molecules typically
induce weak or slower (more gradual) rejection reactions
than do MHC molecules.

MHC: Major histocompatibility
HLA: Human leukocyte antigen
Chinen and Buckley J Allergy Clin Immunol 2010;125:S324-35

• Polymorphism: Each HLA molecule differs from the
other in its amino acid sequence.
• As of March 2017, the total allele number of HLA
loci has reached 16755.
• Linkage Disequilibrium:
• Inheritance of certain alleles at different loci segregate
together more frequently than would be expected by
random assortment within a population
• A1, B8, DR3, DQ2 haplotype in Northern Europeans
• Specific DR allele can be used to predict the associated
DQ allele
MHC: Major histocompatibility
HLA: Human leukocyte antigen

• Every person has two copies of chromosome 6 and possesses two
haplotypes, one from each parent.
• HLA genes are autosomal dominant and co-dominant, the phenotype
represents the combined expression of both haplotypes
Deshpande A. Glob J Transfus Med 2017;2:77-88

HLA typing resolution
Nunes et al. Blood 2011;118(23):e180-3

Nunes et al. Blood 2011;118(23):e180-3
The nomenclature of the HLA locus takes into account the
enormous polymorphism identified by serologic and
molecular methods.

MHC class I VS MHC class II

Rejection VS Graft versus host disease
Recipient Donor
GVHD
Rejection

Grafts are rejected only if they express an MHC type (represented
by green or orange) that is not expressed by the recipient mouse.

Allogeneic MHC molecules of a graft can be presented for recognition
by the recipient’s T cells in two fundamentally different ways
Recognition of Alloantigens by T Cells

How self MHC-restricted T cell can recognize foreign MHC molecules
T cell responses to directly presented allogeneic MHC molecules are
very strong because there is a high frequency of T cells that can
directly recognize any single allogeneic MHC.

Activation and effector functions of alloreactive T lymphocytes
Alloreactive CD4 and CD8 T cells that are activated by graft
alloantigens cause rejection by distinct phenotypes mechanisms.
• CD4: cytokine producing effector cells  cytokine mediated
inflammation, Delayed type hypersensitivity reaction
• CD8: Cytotoxic lymphocyte  killing grafts

In addition to recognition of alloantigen, costimulation of T cells
primarily by B7 molecules on APCs is important for activating
alloreactive T cells.

Activation of alloreactive B cells
and production and functions of alloantibodies
• Antibodies against graft antigens, called donor-
specific antibodies, also contribute to rejection
• Indirect presentation of alloantigens
• Naïve B cells recognize the allogenic MHC molecules 
antigen processing (act as APC)  helper T cell-
dependent activation alloantibodies
• Donor-specific antibodies against non-HLA
alloantigens also contribute to rejection.
• Endothelial cells (express MHC antigens)
• Alloantibody-mediated damage is targeted at the graft
vasculature.

Patterns and Mechanisms of
Allograft Rejection

• Thrombotic occlusion of the graft vasculature
• Onset: within minutes to hours after host blood
vessels are anastomosed to graft vessels
• Mediated by preexisting antibodies in the host
circulation that bind to donor endothelial antigens
• ABO blood group antigens
• Extremely rare now (donor-recipient compatible ABO
types)
Hyperacute Rejection

• Major barrier to xenotransplantation
• The rare instances
• IgG directs against protein alloantigens (MHC
molecules, protein on vascular endothelial cells)
• Risk factors: blood transfusion, previous
transplantation, multiple pregnancies
• May develop slowly (several days) due to low level of
alloreactive antibodies
• If ABO incompatibility between Donor-Recipient
• Depletion of antibodies and B cells

A. Preformed antibodies reactive with
vascular endothelium activate
complement and trigger rapid
intravascular thrombosis and necrosis of
the vessel wall.
B, Hyperacute rejection of a kidney
allograft with endothelial damage,
platelet and thrombin thrombi, and early
neutrophil infiltration in a glomerulus.

Acute Rejection
• Process of injury to the graft parenchyma and blood
vessels mediated by alloreactive T cells and antibodies.
• Onset: several days to a few weeks after
transplantation
• the time needed to generate alloreactive effector T cells and
antibodies in response to the graft
• may occur at much later times, even years after
transplantation
• Types
• Cellular (mediated by T cells)
• Humoral (mediated by antibodies)

A. CD4 + and CD8 + T
lymphocytes reactive with
alloantigens on endothelial
cells in blood vessels and
parenchymal cells mediate
damage to these cell types.
B. Acute cellular rejection
of a kidney with
inflammatory cells in the
connective tissue around
the tubules and between
epithelial cells of the
tubules.
C. Inflammation of a blood
vessel (vasculitis) in acute
cellular rejection, with
inflammatory cells
damaging endothelium.
Acute cellular rejection

Acute antibody-mediated rejection
A. Alloreactive antibodies
formed after engraftment
may contribute to
parenchymal and vascular
injury.
B. Acute antibody-
mediated rejection of a
kidney allograft with
inflammatory cells in
peritubular capillaries.
C. Complement C4d
deposition in capillaries
in acute antibody-
mediated rejection,
revealed by
immunohistochemistry as
brown staining.

Chronic Rejection and
Graft Vasculopathy
• The major cause of the failure of vascularized organ
allografts
• Onset: insidiously during months or years
• May or may not be preceded by clinically
recognized episodes of acute rejection
• Different transplanted organs is associated with
distinct pathologic changes.
• Kidney and heart: vascular occlusion and interstitial
fibrosis
• Lung: thickened small airways (bronchiolitis obliterans)
• Liver: fibrotic and nonfunctional bile ducts.

A. Graft arteriosclerosis
B. The vascular lumen is replaced
by an accumulation of smooth
muscle cells and connective
tissue in the vessel intima.
C. Fibrosis and loss of tubules in
a kidney
A dominant lesion of chronic rejection in vascularized grafts is arterial
occlusion as a result of the proliferation of intimal smooth muscle cells, and
the grafts eventually fail mainly because of the resulting ischemic damage.

Prevention and Treatment
of Allograft Rejection

Method to reduce the
immunogenicity of allograft
• Solid organs transplantation, graft survival after
transplantation varies depending on the source.
• living VS deceased donors
• The survival of grafts from deceased donors is on average
lower than from either related or unrelated living donors
because there is more ischemic damage to organs removed
after death of the donor.
• The major strategy to reduce graft immunogenicity
has been to minimize alloantigenic differences
between the donor and recipient.
• To avoid hyperacute rejection, the ABO blood group
antigens of the graft donor are selected to be
compatible with the recipient.

In kidney transplantation, the larger the number of MHC
alleles that are matched between the donor and recipient,
the better the graft survival.

• In the case of heart and liver transplantation,
organ preservation is more difficult, and potential
recipients are often in critical condition.
• HLA typing is not considered in pairing of potential
donors and recipients,
• The choice of donor and recipient is based on ABO
blood group matching, other measures of immunologic
compatibility and anatomic compatibility.
• In hematopoietic stem cell transplantation,
• HLA matching is essential to reduce the risk of graft-
versus-host disease (GVHD).

• Most HLA haplotype determinations are now
performed by polymerase chain reaction (PCR).
• actual nucleotide sequence, predicted amino acid sequence
• precise molecular tissue typing
• The nomenclature of HLA alleles has changed to reflect
the identification of many alleles not distinguished by
previous serologic methods.
• For example, HLA-DRB1*1301
• sequence 01 allele
• serological HLA-DR13 family
• genes encoding the HLA-DR β1 protein

Patients in need of allografts are also tested for the presence
of preformed antibodies against donor MHC molecules or
other cell surface antigens.
• Two types of tests are done to detect these antibodies.
• The panel reactive antibody (PRA) test, screened for the
presence of preformed antibodies reactive with allogeneic
HLA molecules prevalent in the population.
• The patient's serum are mixed with multiple fluorescently labeled beads
coated with defined MHC molecules.
• Each MHC allele is attached to a bead with a differently colored fluorescent
label.  detect by flow cytometry
• The results are reported as PRA, which is the percentage of the MHC allele
panel with which the patient's serum reacts.
• The cross-matching test will determine when a potential
donor is identified.
• The test is performed by mixing the recipient's serum with the donor's
blood lymphocytes
• Complement is added to the mixture of cells and serum, and if preformed
antibodies, usually against donor MHC molecules, are present in the
recipient's serum, the donor cells are lysed.

Inhibitors T cell signaling pathways
Anti metabolite
Function-Blocking or
Depleting Anti-Lymphocyte Antibodies
Costimulatory Blockade
Immunosuppression to Prevent or
to Treat Allograft Rejection

• The calcineurin inhibitors: Cyclosporine and
Tacrolimus (FK506)
• Inhibit transcription of certain genes in T cells, most notably
genes encoding cytokines such as IL-2.
• Cyclosporine binds with high affinity to a ubiquitous cellular
protein called cyclophilin.
• The complex of cyclosporine and cyclophilin binds to and inhibits
the enzymatic activity of the calcium/calmodulin-activated
serine/threonine phosphatase calcineurin.
• Inhibition of calcineurin  can not activate the transcription factor
NFAT
• Limitation: kidney damage, and some rejection episodes are
refractory to cyclosporine treatment
• Tacrolimus binds to FK506 binding protein (FKBP) and the
complex shares with the cyclosporine-cyclophilin complex the
ability to bind calcineurin and inhibit its activity.

• Rapamycin (Sirolimus) inhibits growth factor–
mediated T cell proliferation.
• Binds to FKBP, but does not inhibit calcineurin.
• Inhibits a cellular enzyme called mammalian target of
rapamycin (mTOR)
• Several growth factor receptor signaling pathways,
including the IL-2 receptor pathway in T cells, as well as
TCR and CD28 signals, activate mTOR through PI3K-Akt,
leading to translation of proteins needed for cell cycle
progression.
• Inhibits effector T cells but does not impair the survival
and functions of regulatory T cells (Tregs)
• mTOR is involved in dendritic cell functions, B cell
proliferation and antibody responses,
• effective in preventing or treating antibody-mediated rejection

• Metabolic toxins that kill proliferating T cells are used
in combination with other drugs to treat graft
rejection.
• Inhibit the proliferation of lymphocyte precursors during
their maturation and also kill proliferating mature T cells that
have been stimulated by alloantigens.
• Azathioprine
• Limitation: toxic to precursors of leukocytes in the bone marrow
and enterocytes in the gut.
• Mycophenolate mofetil (MMF)
• Blocks the activity of inosine monophosphate dehydrogenase,
• Inhibit de novo synthesis of guanine nucleotides
• MMF targets lymphocytes in a relatively specific manner.
• MMF is now routinely used, often in combination with
cyclosporine or tacrolimus to prevent acute allograft rejection.
Anti metabolite

• OKT3
• A mouse monoclonal antibody called that is specific for human CD3
• The first monoclonal antibody used as a drug in humans, but it is no
longer being produced
• Anti-thymocyte globulin
• Polyclonal rabbit or horse antibodies specific for a mixture of
human T cell surface proteins
• Deplete circulating T cells either by activating the complement
system to eliminate T cells or by opsonizing them for phagocytosis.
• Monoclonal antibodies specific for CD25 (α subunit of IL-2 receptor)
• Blocking IL-2 binding to IL-2 receptor
• Anti-CD52 (Alemtuzumab)
• Profoundly deplete most peripheral B and T cells for many weeks
after injection.
• It is administered just before and early after transplantation.
• prolonged state of graft tolerance
Function-Blocking or
Depleting Anti-Lymphocyte Antibodies

• CTLA4-Ig (Belatacept)
• recombinant protein
composed of the
extracellular portion of CTLA4
fused to an IgG Fc domain.
• binds to B7 molecules on
APCs and prevents them
from interacting with T cell
CD28
• as effective as cyclosporine in
preventing acute rejection
• Anti-CD40L antibody
• simultaneous blockade of
both B7 and CD40 appears to
be more effective
• Limitation thrombotic
complications
Costimulatory Blockade

• Plasmapheresis
• circulating antibodies can be removed
• Intravenous immunoglobulin (IVIG) therapy
• binding of the injected IgG to the patient's Fc receptors
on various cell types, thereby reducing alloantibody
production and blocking effector functions of the
patient's own antibodies.
• enhances degradation of the patient's antibodies.
• Anti-CD20 (Rituximab)
• The proteasome inhibitor (Bortezomib)
Drugs Targeting Alloantibodies
and Alloreactive B Cells

• Corticosteroids
• Block the synthesis and secretion of cytokines,
inflammatory mediators
• TNF, IL-1, prostaglandins, reactive oxygen species, and
nitric oxide
• The net result of this therapy is reduced leukocyte
recruitment, inflammation, and graft damage.
Anti inflammatory drugs

Anti–IL-2 receptor
Anti–T cell depleting antibody
High-dose corticosteroid
Calcineurin inhibitor
Antimetabolite
Low-dose steroids
Day 0
Transplantation
Induction therapy Maintenance therapy
Day 2-3
Pre-Transplantation Post-Transplantation
Chronic rejection
• become a more common cause of allograft failure
• more insidious than acute rejection
• much less responsive to immunosuppression than is acute rejection

• Abnormal defense against viruses and other
intracellular pathogens.
• Reactivation of latent herpes viruses: CMV, HSV, VZV
• prophylactic antiviral therapy for HSV
• Risk for a variety of opportunistic infections:
• PCP, Histoplasmosis, Toxoplasmosis, Cryptosporidium,
Microsporidium
• Risk for development of cancer
• skin cancer
• HPV  uterine cervical carcinoma
• EBV  lymphomas  Post-transplantation lymphoproliferative
disorders (PTLDs)
Immunosuppressive therapy leads to increased
susceptibility to various types of infections and
virus-associated tumors.
The major limitation: tolerated doses, toxicity to cells

• Costimulatory blockade
• not induce long-lived tolerance
• Hematopoietic chimerism
• recipient becomes a chimera
• limitation: risks of hematopoietic stem cell
transplantation, appropriate donors
• Transfer or induction of Tregs.
• some success reported in recipients of hematopoietic
stem cell transplants (Tregs reduce GVHD)
Method to induce
Donor-Specific Tolerance

Hematopoietic Stem Cell
Transplantation

The Nobel Prize in
Physiology or Medicine 1990
“….Thomas was successful in
transplanting bone marrow cells
from one individual to another.
Bone marrow transplantation can
cure severe inherited disorders
such as thalassemia and
disorders of the immune system
as well as leukemia and aplastic
anemia.
Murray's and Thomas'
discoveries are crucial for those
tens of thousands of severely ill
patients who either can be cured
or be given a decent life when
other treatment methods are
without success. ”
E. Donnall Thomas, MD
1920-2012

• Treat lethal diseases caused by intrinsic defects in
one or more hematopoietic lineages in a patient.
• HLA discovery in 1968
• Since 1955, more than 240,000 bone marrow
transplantations have been performed worldwide
at 450 centers in 47 countries for the treatment of
more than 50 different fatal diseases.
• SCID in 1968
Indications, Methods and
Immune Barriers in HSCT

• Several unique features that are not
encountered with solid organ
transplantation.
• The mechanisms of rejection of HSCs are
not completely known, but in addition to
adaptive immune mechanisms.
• Irradiated F1 hybrid mice reject bone
marrow cells donated by either inbred
parent “Hybrid resistance”
• Depletion of recipient NK cells with anti–
NK cell antibodies prevents the rejection
of parental bone marrow cells.
Allogeneic HSCs are rejected by even a minimally
immunocompetent host, and therefore, the donor and
recipient must be carefully matched at all MHC loci.
HSCs may be rejected by NK cells. Yes

Recognition of self class I MHC inhibits the activation of NK
cells, and if these self MHC molecules are missing, the NK
cells are released from inhibition
Hybrid resistance is probably due to host NK cells reacting
against bone marrow precursors that lack class I MHC
molecules expressed by the host.

Composition of HSCT
-6 -5 -4 -3 -2 -1 0 +14 +21 +100
Conditionining
HSCT graft
GVHD prophylaxis
Supportive care
Patient
Diseases
(Donor)
1
2
3
4
5
Adapted from Mohamed Monty, MD presentation

•Bone marrow
•Peripheral blood
•Umbilical cord blood
Type of stem cells graft by sources
• Multiple aspirations along the iliac crests under general anesthesia
• 500 mL- 1 L depended on the type of transplant and on the weight
of the recipient
• HLA-identical transplantation  injected intravenously without
further manipulation into a central line in the recipient
• Mismatched transplantation T-cell depleted and injected
intravenously

• Peripheral blood stem cell collection
Mobilization Aphaeresis
G-CSF

• Umbilical cord blood stem cells collection
• Collected in heparinized medium and stored in liquid nitrogen, and
small aliquots are preserved for HLA typing
• Thawed and injected into the recipient without further manipulation
• lower severity of GVHD without full HLA matching

Donor Minimum acceptable HLA-match
Related • Antigen level: HLA-A,B, DRB1(6/6)
Unrelated
(BM,PBSC)
• Allele level: HLA-A,B,C, DRB1 (8/8)
• 7/8 match result in decrease survival and
increase significant GVHD by 5-10%
Unrelated
(UCB)
• 6/6: cell dose > 2 x 107 TNC/kg
HLA matching consideration

• Recipients
• Pre transplantation: chemotherapy, immunotherapy, or
irradiation
• Post transplantation: stem cells repopulate the recipient's
bone marrow and differentiate into all of the hematopoietic
lineages.
• Indication
• Leukemias
• graft-versus-tumor effect
• Inherited mutations in genes affecting only cells derived from
HSCs
• ADA deficiency, X-linked severe combined immunodeficiency
disease
• Hemoglobin mutations: beta-thalassemia major and sickle cell
disease
Indications, Methods and
Immune Barriers in HSCT

Donor selection and
manipulation of the graft
• HSCT from a related HLA-identical donor
• Best for rapid engraftment andimmune reconstitution
• The mature T cells contained in the graft provide a first
line of immune reconstitution after transplant
• Rapid increase circulating T lymphocytes 2 weeks after
HSCT
• HSCT from a haploidentical donor
• No such donor is available.
• Based on the ability of donor-derived stem cells to
repopulate the recipient’s vestigial thymus and give rise
to fully mature T lymphocytes
• life-saving procedure of SCID infants
Rich RR, et al. Clinical Immunology principles and practice. 3rd edition

• HSCT from matched unrelated donors
• Increasingly used to treat severe primary immunodeficiencies
• Bone Marrow Donors Worldwide (BMDW) registry
• 3–4 months to identify a MUD
• Preparative chemotherapy regimen in the recipient (even in
the case of SCID) and graft versus-host prophylaxis
• HSCT using unmanipulated cord blood
• Lower risk of GvHD than with MUD
• Based on the urgency of the transplant, the cell dose
required, and the number of HLA disparities
• Requires pre-transplant conditioning and GvHD prophylaxis,
irrespective of the underlying disease
Donor selection and

• T-cell depletion
• Soybean lectin: agglutination of mature marrow cells
and removed by sedimentation
• E-rosetting (with sheep erythrocytes) and density
gradient centrifugation
• Incubation of the marrow with monoclonal antibodies to
T lymphocytes plus complement; Campath-1G, Leu 1
• Positive selection of CD34+ cells using monoclonal
antibody affinity
Donor selection and

• Conditioning regimen toxicity
• affect several organs e.g. busulfan-lung damage, veno-
occlusive disease, anemia, thrombocytopenia, and
leukopenia
• Graft rejection
• Graft-versus-host disease
• Infections
Complications of HSCT

• GVHD is caused by the reaction of grafted mature T cells in
the HSC inoculum with alloantigens of the host.
• Occur when the host is immunocompromised and
therefore unable to reject the allogeneic cells in the graft.
• Most cases due to minor histocompatibility antigens of the
host
• GVHD in solid organs
• small bowel, lung, liver  significant numbers of T cells are
transplanted
• GVHD is the principal limitation to the success of bone
marrow transplantation.
• Immediately after HSC transplantation, immunosuppressive
agents prophylaxis against the development of GVHD.
Immunologic Complication of HSCT
Graft-Versus-Host-Disease
Cyclosporine, tacrolimus, sirolimus

• Epithelial cell death in the skin, liver (mainly the biliary
epithelium), and gastrointestinal tract.
• Manifestation: rash, jaundice, diarrhea, and gastrointestinal
hemorrhage.
• May be fatal.
Acute GVHD
• NK cells are often attached to the dying epithelial cells.
 suggesting that NK cells are important effector cells of acute GVHD.
• CD8+CTLs and cytokines also appear to be involved in tissue injury in acute GVHD
Abbas AK. Cellular and Molecular Immunology 9th edition, 2018

• Response to ischemia caused by vascular injury
• Symptoms persist or appear after 100 days
• Fibrosis and atrophy of one or more of the same
organs, without evidence of acute cell death
• Leads to complete dysfunction of the affected
organ
• Lungs  bronchiolitis obliterans
Chronic GVHD

• The relationship of chronic GVHD to acute GVHD is
not known.
• chronic GVHD  to acute loss of epithelial cells
• chronic GVHD  without evidence of prior acute GVHD
• An alternative explanation is that chronic GVHD
• Risk factors
• Acute GVHD
• Older age of the recipient
• Transplantation from a multiparous female donor into a
male recipient
• Minor histocompatibility incompatibility
Chronic GVHD

• Prevention
• Fully matched donor
• T-cell depleted HLA-mismatched donor
• Pharmacological GvHD prophylaxis
• Cyclosporine A daily for 6 months or
• Methotrexate (15 mg/m2 on the first day, and then 10 mg/m2
at day 3, 6 or
• combination ATG
Acute and Chronic GVHD

• Commonly treated with intense immunosuppression, such
as high doses of steroids
• Many patients do not respond well
• because these treatments target only some of many effector
mechanisms at play in GVHD
• some treatments may deplete Tregs
• Experimental therapies in development
• anti-TNF antibodies, Treg transfer
• tumor antigen-specific adoptive T cell therapy
• Patients with HSC preparations rigorously depleted of
mature T cells and NK cells to reduce the risk of GVHD
• decrease the graft-versus-leukemia effect
• T cell–depleted HSC preparations also tend to engraft poorly.
• mature T cells produce colony-stimulating factors
Acute and Chronic GVHD

• Mis-matched
• includes haplo-identical from relative
• Matched Unrelated
• Unrelated Umbilical Cord Blood
• Matched 1st degree relative
• Syngeneic
Risk for GVHD
Highest
Lowest

• The transplant recipients may be unable to regenerate
a complete new lymphocyte repertoire.
• Radiation therapy, chemotherapy  deplete the patient's
memory cells and long-lived plasma cells
• Susceptible to viral infections, especially
cytomegalovirus infection, and to many bacterial and
fungal infections.
• More severe than those of conventionally
immunosuppressed patients
• antibiotics, antiviral prophylaxis, antifungal prophylaxis
• maintenance IVIG infusions
• immunized against common infections
Immunodeficiency after HSCT
HSC transplantation is often accompanied by clinical immunodeficiency.

Hematopoietic Stem Cell
Transplantation for the treatment of
Primary Immunodeficiency Disorders

HSCT for SCID
• Immune suppression is not required
• No conditioning regimen is necessary in related
HLA-identical donor
• US centers adopt same policy for T cell-depleted
mismatched HSCT
• European centers tend to use conditioning
regimens prior to mismatched or MUD HSCT,
particularly in SCID with residual autologous NK

Survival following HSCT for SCID
Related HLA-identical, MUD, and T cell-depleted haploidentical
HSCT were 100%, 94%, and 52%, respectively
improved over the years

• Younger age at transplantation leads to superior
survival
• Among 38 infants who were treated by Buckley and
collaborators before 3.5 months of age, 37 (97%) have
survived
• In Europe, among infants with SCID who received HLA-
identical transplantation, survival was clearly better
when HSCT was performed at less than 6 months of age
(85% survival rate) than at 12 months or more (survival
rate 53%).
• Co-trimoxazole prophylaxis for recipients
• Absence of pre-transplant pulmonary infection
among recipients
• Type of SCID
Several factors influence survival after HSCT for SCID

• Survival following related HLA-mismatched HSCT is better in infants
with B+ SCID than with B− SCID (64% vs 36%, respectively).
• The poorer outcome in infants with B− SCID may reflect the
presence of autologous NK cells detectable in most of these infants.

• HSCT from MUD has been shown to be an effective
treatment for SCID.
• sustain engraftment and better immune reconstitution
than with T cell-depleted haploidentical HSCT.
Complications following HSCT for SCID
• Infections, GvHD, BLPD (B-cell lymphoproliferative disease)
• Immune dysregulation and autoimmunity
% Survival rate
MUD HSCT HLA-identical
HSCT
Haploidentical-
HSCT
Canada center 80% (33/41) 92% (12/13) 52% (21/40)
Japan center 100% (7/7) - 12.5% (1/8)

• The effectiveness of HSCT in SCID
• The normalization of the number and function of T
lymphocytes
• Reconstitution differs substantially depending on
the type of transplantation.
• The kinetics of T-cell reconstitution influenced by
the recipient’s age.
• Early transplantation(<3.5months of age) leads to
superior thymic output
Quality and kinetics of T-cell immune reconstitution

• Quantification of TRECs
• Assess engraftment of bona fide stem cells and to monitor the
persistence of immunity
• Decline by 10 years
• Possible that the SCID thymus is not able to sustain active
thymopoiesis for as long as a normal thymus

Related HLA-identical HSCT
• The unmanipulated graft contains mature T lymphocytes
• expanded in 2 weeks
• Oligoclonal, have a memory (CD45R0) phenotype
• Fully competent, and provide the recipient with functional immunity
MUD HSCT
• Present mature T cells
• Conditioning regimen partly impairs immune development
• Naive (CD45RA+ CD31+) T lymphocytes appear in 3–4 months
• Number tends to peak 1 year after HSCT

• Depend on the nature of the genetic defect
• B+ SCID, IL7RA gene defect usually develop normal
B-cell immunity after HSCT even if no donor-
derived B cells are present
• γc or JAK3 deficiency (both of which compromise
B-cell function) often remain dependent on
immunoglobulin substitution
• More limited data are available about
reconstitution of NK cell function
Reconstitution of B- and NK-cell immunity

SY Pai et al. N Engl J Med 2014;371:434-46
The Primary Immune Deficiency Treatment Consortium (PIDTC)
a collaborative network of institutions in North America

• Study design: retrospective, multicenter
• Participants: 240 infants with SCID who had received transplants at 25
centers during a 10-year period (2000 through 2009)
• Data collection
• Demographic data, Immunologic profile, infection history
• Transplantation: conditioning regimen, donor type, degree of HLA match, cell
source, method of T-cell depletion, GVHD prophylaxis
• Immune Reconstitution
• Data collected at 100 days, at 6 months, and at 1, 2 to 5, and 6 to 10 years after
transplantation
• CD3+ T cells, CD19+ or CD20+ B cells, and CD3−CD56+ or CD16+CD56+ NK cells
• PHA
• IgG, IgA, and IgM
• treatment with IVIG
• whole-blood and lineage-specific chimerism

• Children with classic SCID diagnosed at birth or before the onset of
infection who receive transplants from mismatched related donors,
transplants from unrelated donors, or cord-blood transplants soon
after diagnosis have more than a 90% probability of survival with T-
cell and variable B-cell immune reconstitution.
• The mortality  active infection at the time of transplantation
• For such patients who did not receive transplants from matched
donor siblings, the survival rate was highest among
• T-cell–depleted grafts from mismatched
• related haploidentical donors without undergoing conditioning
• Transplants from donors other than matched siblings were associated
with excellent survival among infants with SCID identified before the
onset of infection.
• All available graft sources are expected to lead to excellent survival
among asymptomatic infants. SY Pai et al. N Engl J Med 2014;371:434-46

• Residual T cell-mediated immunity
• obstacle to engraftment
• pre-transplant conditioning regimen
• even when an HLA-identical donor is available.
• Results of T cell-depleted haploidentical transplant are
not particularly good.
• These disorders rarely represent a medical emergency
and often permit longer survival.
• The decision whether to attempt HSCT for
immunodeficiencies other than SCID must be based on
• patient’s clinical history and quality of life
• the effectiveness of alternative and more conservative
approaches
HSCT for immunodeficiencies
other than SCID

Transplantation immunology

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