2.5: Stem Cell Transplantation Flashcards
STEM CELL TRANSPLANTATION
Stem cell transplantation is a 2-step process involving eradication of the patient’s blood cells then replacing them with donor stem cells:
• Chemotherapy and/or radiotherapy to eradicate the haematopoietic and immune systems → prevents immune rejection and graft-versus-host disease (GVHD)
• Donor cells may be allogeneic stem cells (from other individuals) or autologous stem cells (previously harvested portion of patient’s own stem cells)
DONOR TYPES
- Autologous (Patient’s own stem cells) : Multiple myeloma*, Hodgkin’s disease, non-Hodgkin’s lymphoma
→ Patients with allogeneic SCT had a worse short-term result compared to those with autologous SCT (standard treatment) → tandem transplant recommended (2 autologous SCTs 6 months apart) but may be riskier
- Syngeneic: From identical twin
- Allogeneic (________________ (1st choice), Matched unrelated HLA donor (MUD), Umbilical cord blood*,
Haploidentical (half-matched), Mismatched transplants) AML, MDS, ALL
→ Preferred for leukaemias as giving autologous transplants means a possibility of giving some of the leukaemia cells back (also the ________________ in allogeneic transplants which could eradicate the cancer)
*Umbilical cord blood is considered an allogeneic transplant as the immune cells in the cord blood are naïve in terms of immunogenicity (technically not the patient’s own).
HLA-matched sibling;
graft-vs-leukaemia effect
Allogeneic SCT
- Stem cells are removed from the donor + Patient receives __________________- (± total body irradiation) to destroy blood-forming cells
- Stem cells from donor ± _________________ (reduces GVHD) → infused IV + Patients receive supportive therapy and prophylaxis against GVHD (immunosuppressants like ____________________)
- Administered fresh
- Advantages: Graft-versus-tumour/leukaemia effect
Mechanism of cure
- Non-malignant disorders:
• Replaces stem cells (____________)
• Replaces defective haematopoiesis (____________)
• Replaces pluripotent lymphohaematopoietic progenitors (congenital immunodeficiency, genetic errors of metabolism)
- Malignant disorders:
• ____________ effect of conditioning (chemotherapy/radiotherapy before SCT also kills tumour cells)
• Graft-versus-tumour effect (exerted by transplanted donor ____________ against malignant tissues)
high-dose chemo/radiotherapy;
T cell depletion;
cyclosporin, methotrexate
aplastic anaemia;
sickle cell anaemia;
Anti-tumour;
T cells and NK cells
[Autologous SCT]
- Stem cells are removed from the patient + Patient receives high-dose chemo/radiotherapy (± total body irradiation) to destroy blood-forming cells
- Stem cells from patient ± _________________ (removes residual tumours) → infused IV
*Patient does not require immunosuppressants as graft is “self”
- Administered after _________________
- Mechanism of cure: Ability to give escalated doses of chemotherapy to cure disease -> infusion of autologous SCs (removed prior) to overcome ________________ (cure lymphoma/ prolong survival in myeloma)
Advantages
GVHD is not present
tumour purging;
cryogenic preservation;
dose-limiting toxicity of bone marrow suppression
HLA SYSTEM
The main function of HLA (found on cell surface membranes) is to direct T cell responses:
• HLA typing: from WBCs in ___________ or mucosal cells in the _____________
o Antigen specificity defined by ______________ (e.g. HLA-A2)
o Alleles determined by DNA sequencing (e.g. HLA-A01:01, HLA-A02:01)
• Ideal condition is to match 2 alleles for HLA-A, -B, -C, -DR (8 of 8 match) or including HLA-DQ (10 of 10 match) between the donor and recipient:
o Greater HLA mismatch → greater immune response between transplanted cells → GVHD (graft rejection)
• ___________________ transplants: donor is half-matched for the patient (usually a family member) → when a close HLA match cannot be found
o One set of loci is inherited from each parent (inheritance of full loci is closely linked) → 25% chance for siblings to be HLA-identical
o Parents are always haploidentical, while siblings have 50% chance
o Inheritance of HLA is independent of gender and blood group
peripheral blood;
buccal mucosa;
serological typing;
Haploidentical (half/partially-matched)
STEM CELL COLLECTION
PBSCT (peripheral blood)
- Days 1 – 4: ___________________ given as course of injections 10mg/kg/day for 4 – 6 days (PB contains too few haematopoietic stem cells for collection for transplantation) until WCC rises
• __________- (inhibitor of stem cell adhesion in bone marrow) given if mobilisation of stem cells likely to be inadequate
• Usually done in ______________ due to previous chemotherapies
- Days 5 – 6: harvesting from vein in arm of donor (patient/another individual) → ______________ (removes mononuclear stem cells) → blood returned to donor through vein in other arm
• Process takes few hours (depending on efficiency of stem cell mobilisation) for enough mononuclear stem cells
• Repeated collections may be required for up to 3 days - Adequacy of collection: _________________ of body weight of the recipient required for transplantation
*Refusal of G-CSF (due to possible adverse reactions) or failure of PBSC collection due to inadequate mobilisation → BMSCT
G-CSF (growth factor);
Plerixafor;
autologous transplants;
apheresis machine;
CD34 positive cell count > 2x106/kg
BMSCT (bone marrow)
- Donor given general anaesthetic → _____________ of bone marrow harvested from pelvis → marrow is anticoagulated
• Adequacy of collection: mononuclear cell count 2-4 x 108/kg of body weight of recipient
500 – 1200 mL
UCBT (umbilical cord blood)
- Foetal blood (rich source of haematopoietic stem cells) is collected from cord blood:
• Umbilical cord clamped and cut after delivery of baby → residual umbilical cord blood collected from _______________ (while waiting for delivery of placenta) (takes few minutes) → cord blood collection completed when placenta expelled
• Small numbers of stem cells collected from single cord → most useful for children who do not have fully matched siblings or unrelated donors
o ______________ may be required to obtain sufficient stem cells for adult recipients
• HLA-matching for cord blood transplantation less stringent (cells naïve in terms of immunogenicity):
o Immune reconstitution slower following UCBT
umbilical vein;
Double cord donations
After collection, the stem cell harvest is processed by reduction of product volume, removal of red cells and concentration of mononuclear cells:
• Purging (removal) of T lymphocytes using antibodies (to reduce the risk of GVHD)
• Purging of residual malignant cells via _________________
• _____________ are selected from both types (allografts and autografts)
chemotherapy/antibodies (in autografts) ;
CD34+ stem cells
Chemotherapy or total body irradiation (TBI) is done for the patient prior to infusion of _________________:
• To eradicate patient’s haematopoietic and immune system and any residual malignancy (if present for both allografts and autografts)
• To suppress host immune system → prevent rejection of foreign stem cells
(allogeneic) haematopoietic stem cells
Myeloablative
- Administration of _____________ and total body irradiation (before transplant on day 0):
• Intensive chemoradiotherapy: anti-tumour activity; decreases host haematopoiesis and immunity
• Immunosuppressive drugs (e.g. cyclosporin, methotrexate post-transplantation): prevent GVHD
• Engraftment of donor stem cells essential to rescue patient from ___________________
Main complications: _________ (due to intensive cytotoxic therapy), opportunistic infection (during period of __________), GVHD
Eradication: ____________________ + graft-vs-leukaemia effect
intensive chemotherapy;
lethal haematopoietic toxicity;
organ damage;
neutropenia;
intensive chemoradiotherapy
Non-myeloablative
- Administer __________________ and total body irradiation (before transplant on day 0):
• Mostly used for elderly patients or patients who cannot tolerate high dose chemotherapy and irradiation in myeloablative conditioning
• Less intensive; sufficiently immune-suppressive for engraftment of donor stem cells
• Immunosuppressive drugs (e.g. cyclosporin, mycophenolate mofetil) to prevent graft rejection and GVHD
Main complications: GVHD, opportunistic infections (due to immunosuppressive therapy)
Eradication: graft-vs-leukaemia effect only
fludarabine (chemotherapy)
POST-TRANSPLANT ENGRAFTMENT & IMMUNITY
After stem cell transplantation, there is a period of severe pancytopenia (1 – 3 weeks):
• Followed by initial recovery of _____________ then the __________ (engraftment is quicker in PBSCT)
• Profound immunodeficiency (3 – 12 months) with low CD4 T helper cell count
• Patient’s blood group and antigen-specific immunity becomes that of the donor after about 60 days
• _______________ is essential after all SCTs
neutrophils and monocytes;
platelet count;
Revaccination
COMPLICATIONS
Complications are more common in allogeneic transplants than autologous transplants (due to high dose chemotherapy with stem cell rescue):
• Complications of autologous SCT are similar to chemotherapy (higher incidence of _________________)
Within first 100 days
- Organ toxicity, idiopathic pneumonia, acute GVHD, infections (bacterial, fungal, herpes, CMV, pneumocystis pneumonia), graft failure
- Use of laminar air flow, positive pressure rooms to reduce infection risk
- Prophylactic drugs to prevent fungal, HSV, ______________ infections
- Monitor _____________ + pre-emptive treatment with antivirals (if CMV reactivates)
→ measure exposure before transplantation (but in Singapore almost 100% of population is CMV-positive → not measured
After first 100 days
- Chronic GVHD, late effects of transplant (e.g. ___________-, infertility, second malignancies)
- Lifelong follow-up of recipient (relapse may occur anytime → though less common after 2 years and risk decreases with time)
mucositis and organ toxicity;
pneumocystis pneumonia (PCP);
CMV DNA titres;
cataracts;
The two possible outcomes following an SCT is cure and long-term survival (with or without morbidity) and death (significant proportion of patients):
• Main cause of long-term morbidity after allogeneic transplant is __________
• Survival after transplant at 5 years is 30 – 65% depending on the disease
Autologous SCT
- _________________ (70%)
- Non-relapse mortality (e.g. organ toxicity, infections, idiopathic pneumonia) (30%)
- Procedure-related mortality (<5%)
Allogeneic SCT
- Relapse of underlying disease (35 – 40%)
- Non-relapse mortality (e.g. GVHD, organ toxicity, infections, idiopathic pneumonia) (60 – 65%)
GVHD;
Relapse of underlying disease
GRAFT-VERSUS-HOST DISEASE (GVHD)
- GVHD occurs when donor immune cells (mainly T cells) recognise recipient host cells as foreign tissue, causing an immune reaction leading to disease in the host:
• Classic acute GVHD: Present within 100 days of haematopoietic cell transplant with features of acute GVHD. Diagnostic features of chronic GVHD are absent
• ________________: Present after 100 days with features of acute GVHD. Diagnostic features of chronic GVHD are absent
• Classic chronic GVHD: Present any time post-HCT with features of chronic GVHD. Diagnostic features of acute GVHD are absent
• Overlap syndrome (acute-on-chronic): Present any time post-HCT with features of both acute and chronic GVHD
Persistent, recurrent, late onset acute GVHD
KEY FACTORS
For the patient to develop GVHD post-transplant, the following factors are necessary (all present in allogeneic transplants during the first 100 days):
1. Graft contains ___________________-
2. Host possesses _____________ lacking in/foreign to graft → host cells stimulate donor cells via specific antigenic determinants
3. Host is incapable of mounting reaction against graft for sufficient period of time to allow graft cells to attack host
immunologically competent cells ;
transplantation antigens
ACUTE GVHD
Acute GVHD is a reaction to the stem cell transplantation occurring within 100 days:
Pathophysiology
1. Conditioning (radiation/chemotherapy): damage and activation of host tissues (especially intestinal mucosa)
• To host tissues: release of inflammatory cytokines (_______________)
• To intestinal mucosa: translocation of LPS from intestinal lumen into circulation → secretion of inflammatory cytokines TNF-α, IL-1 from _________
• Inflammatory cytokines increase expression of MHC antigens and adhesion molecules on host tissues → enhance recognition of ____________________ by mature donor T cells
2. Donor T cell activation: Th1 cells secrete __________ which further activates monocytes and macrophages
3. Cellular and inflammatory effectors: activated macrophages, CD4 and CD8 T lymphocytes secrete inflammatory cytokines → trigger _____________
• Damage to GIT by inflammatory cytokines → amplifies release of ________ → cytokine storm (characteristic of acute GVHD) → amplifies local tissue injury and promotes inflammatory response
TNF-α, IL-1, LPS;
macrophages
major/minor histocompatibility antigen (HCA);
IL-2 and IFN-λ;
target cell apoptosis
LPS
[Acute GVHD] Clinical manifestations - Skin: \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ - Gut: abdominal cramps with diarrhoea - Liver: jaundice *Diagnosis is made with the above features within 2 – 3 weeks after haematopoietic cell transplantation (severity determined by the degree of involvement of various organs → prognostic significance)
Prophylaxis: immunosuppressants (e.g. cyclosporin, tacrolimus along with mycophenolate, methotrexate, prednisolone)
- Definitive treatment: ___________________(effective in most cases)
classic maculopapular rash;
high dose corticosteroids
[CHRONIC GVHD]
Pathophysiology
- Process of chronic GVHD is similar to autoimmune disease (with features of autoimmune disease developing):
• Features of scleroderma, ___________, ____________ (inflammatory condition affecting skin, hair, nails, mucous membranes → purplish itchy flat-topped bumps developing over several weeks)
• Immune system becomes impaired → risk of infections
• Malabsorption, pulmonary abnormalities are frequent
Clinical manifestations
- Cutaneous: dyspigmentation, scleroderma, morphea, alopecia, onychodystrophy, lichen planus (affects almost any organ)
- Hepatic: ________, hepatomegaly (rare)
- Haematological: immune-mediated thrombocytopenia, immune-mediated haemolytic anaemia
- GI: diarrhoea, anorexia, weight loss, odynophagia (painful swallowing), dysphagia, abdominal pain
- Immunodeficiency: CMV disease, varicella reactivation, fungal disease, oral thrush, sinusitis, streptococcal pneumonia
- MSK: scleroderma, fasciitis, myositis, weakness, cramps, joint contractures
- Performance status: disability, depression, anxiety
- Pulmonary: dyspnoea on exertion, hypoxaemia, fatigue, cough, wheezing
- Ocular: ocular “sicca”, keratoconjunctivitis, cataracts (steroid-related), photophobia
- Oral: lichenoid changes, xerostomia
- Vaginal: vaginal dryness, vaginal strictures
Sjogren’s syndrome;
lichen planus;
jaundice;
[Chronic GVHD]
Treatment
- Corticosteroids + second-line drugs (cyclosporin, rituximab, sirolimus, mycophenolate mofetil, extracorporeal photopheresis)
• __________________: blood treated with photosensitising agent then irradiated with specific wavelength of light to achieve effect
• Response may be poor (chronic GVHD is the main cause of morbidity after SCT)
Extracorporeal photopheresis
