ABO mismatch AlloSCT

1. Transfusion Discussion Session Meeting
ABO Mismatch in
Allogeneic Stem Cell Transplant

2. Case report

3. Case – Miss N.A.
• 26yo lady
• Diagnosis – Ph+ B-cell Acute Lymphoblastic Leukaemia (B-ALL)
• Presented with anaemic symptoms x 1 month
• FBC – Hb 7.4 / TW 45.9 / Plt 106
• FBP – 80% blast

4. Case report - Miss N.A.
• Diagnostic bone marrow exam (17/1/23)
• Aspirate – Hypercellular, >90% blast which are small to moderate in size with
high N:C ratio
• Trephine – Diffuse marrow infiltration by blast cells expressing strong CD34,
CD79a, TdT and partial CD33, and lacking CD20, CD3, CD13 and MPO
expression.
• Flow cytometry – consistent with B-ALL

5. Treatment
• GMALL induction (20/1/23)
• BM reassessment
• Aspirate and Trephine HPE – Morphological remission
• Flow cytometry – 0.6% cluster of cells with a leukaemia phenotype seen at diagnosis
consistent with residual disease
• HyperCVAD A1 (7/3/23)
• BM reassessment
• Cells with leukaemia phenotype are not detected – MRD negative
• Imatinib – started on 9/3/23
• Pulse Dexa-Doxo-Vincristine x 2 (28/3/23, 18/4/23)

6. HLA typing

7. Transplant work-up

8. Transplant work-up
Recipient – 26yo Female
• Blood group – O Positive
• RBC antibody screen – negative
• Viral screen
• CMV IgG – Reactive
• Hep B s Ag – Non-reactive
• Hep B core Ab – Non-reactive
• Anti-HCV – Non-reactive
• HIV1/2 – Non-reactive
• EBV IgG - Reactive
• VZV IgG – Reactive
• HSV1 IgG – Reactive
• HSV2 IgG – Non-reactive
• Toxo IgG – Non-reactive
Donor – 34yo Male
• Blood group – A Positive
• RBC antibody screen – negative
• Viral screen
• CMV IgG – Reactive
• Hep B s Ag – Non-reactive
• Hep B core Ab – Non-reactive
• Anti-HCV – Non-reactive
• HIV1/2 – Non-reactive
• EBV IgG - Reactive
• VZV IgG – Non-reactive
• HSV1 IgG – Reactive
• HSV2 IgG – Reactive
• Toxo IgG – Non-reactive

9. Transplant work-up
Recipient – 26yo Female
• Blood group – O Positive
• RBC antibody screen – negative
• Viral screen
• CMV IgG – Reactive
• Hep B s Ag – Non-reactive
• Hep B core Ab – Non-reactive
• Anti-HCV – Non-reactive
• HIV1/2 – Non-reactive
• EBV IgG - Reactive
• VZV IgG – Reactive
• HSV1 IgG – Reactive
• HSV2 IgG – Non-reactive
• Toxo IgG – Non-reactive
Donor – 34yo Male
• Blood group – A Positive
• RBC antibody screen – negative
• Viral screen
• CMV IgG – Reactive
• Hep B s Ag – Non-reactive
• Hep B core Ab – Non-reactive
• Anti-HCV – Non-reactive
• HIV1/2 – Non-reactive
• EBV IgG - Reactive
• VZV IgG – Non-reactive
• HSV1 IgG – Reactive
• HSV2 IgG – Reactive
• Toxo IgG – Non-reactive

10. Summary
• 26yo lady with B-ALL in CR1, MRD negative
• Matched Sibling Donor Allogeneic Stem Cell Transplant (MSD
AlloSCT).
• Gender mismatch – Male to Female
• Major ABO blood group mismatch – A+ to O+
• CMV concordant – both CMV+
• Conditioning regimen – Busulphan-Cyclophosphamide (Myelo-
ablative)
• GvHD prophylaxis – Cyclosporine-Methotrexate

11. ABO Mismatch
in Allogeneic Stem Cell Transplant

12. Stem cell transplant - Background
Autologous vs Allogeneic

13. Conditioning intensity

14. AlloSCT - considerations
Donor options
• HLA‐matched sibling
• HLA-matched unrelated donor
(MUD donor)
• Haploidentical donor
• Umbilical cord blood (UCB)
Graft sources
• Peripheral blood (PB).
• Bone marrow (BM).
• Umbilical cord blood (UCB)

15. ABO mismatch in AlloSCT
• HLA system is located on the short arm of chromosome 6 on band
6p21
• ABO system are expressed on chromosome 9 at 9q34.
• Hence, ABO are independent of HLA.
• ~40–50% of allo-HSCT are ABO mismatched.

16. ABO compatibility in AlloSCT – 4 scenarios
• ABO compatible
• Major ABO mismatch
• Minor ABO mismatch
• Bi-directional ABO mismatch

17. Major ABO mismatch
• Recipient has isoagglutinins directed against the corresponding A or B
antigens on donor RBCs

18. Minor ABO mismatch
• Donor has isoagglutinins directed against the corresponding A or B
antigens on the recipient’s RBCs

19. Bidirectional ABO mismatch
• Both Recipient and Donor have isoagglutinins against each other

20. Does it matter?
• Does not seem to adversely affect OS, TRM, or severe acute GVHD.
• However, there are complications that should be identified and
managed accordingly.

21. Major ABO mismatch

22. Major ABO mismatch – Issues
• Hemolysis of red cells at the time of graft infusion
• Delayed red cell engraftment
• Pure red cell aplasia (PRCA)

23. RBC hemolysis at the time of stem cell infusion
• Acute hemolytic transfusion reactions at the time of stem cell
infusion
• Especially when the graft contains a significant volume of RBCs e.g. as
in unmanipulated marrow grafts.
• Depends on the quantity of infused red cells

24. Pure red cell aplasia (PRCA)
• Residual recipient plasma cells produce isohemagglutinins against
donor erythroid precursor cells  reticulocytopenia  PRCA
• Usually occurs ~30 to 90 days post-HSCT
• Incidence 8 – 26% of major ABO-mismatched HSCTs.

25. Pure red cell aplasia (PRCA)
• PRCA often resolves within a few weeks to months.
• Other treatments - erythropoietin, steroids, plasma exchange,
rituximab, and donor lymphocyte infusions

26. Preventive strategies
Either
1. Reduce the RBC volume
2. Reduce the titer of incompatible recipient isohemagglutinins.

27. RBC depletion
EBMT guideline 2019
• Recipient anti-donor isoagglutinin titer ≥1:32
• PBSC graft - red cell contamination should be kept <20 mL
• BM graft - RBC depletion must be performed
• Recipient anti-donor isoagglutinin titers are low ≤1:16
• PBSC graft - no manipulation is required
• BM graft - RBC depletion can be considered, but not
mandatory

28. RBC depletion
• Methods
• Manual Centrifugation
• Density Separation using HES / density gradient solution
• Automated Apheresis Instruments
• Disadvantage - reduce the overall stem cell content of the product

29. Reducing the titer of incompatible recipient
isohemagglutinins.
Method #1 – Plasma exchange
• Double filtration plasmapheresis (DFPP) is a newer technique
in which plasma is not entirely removed, only the antibodies,
using special filters.

30. Reducing the titer of incompatible recipient
isohemagglutinins.
Method #2 – Donor-type FFP transfusion
• ABO antigens are secreted into the plasma
• Infusion of donor-type FFP positive in A or B antigens aim to
neutralize respective isohemagglutinins

31. Reducing the titer of incompatible recipient
isohemagglutinins.
Method #3 – Donor-type RBC transfusion
• “When isohemagglutinin titers were 1:32 or higher, donor-type
packed red blood cell was divided into 4 aliquots, irradiated and
administered over 4 days at incremental volumes.
• Patients were observed for hemolytic reaction, and if no
reaction, bone marrow was infused without manipulation”

32. Preventive strategies - Others
• ABO matching
• ABO matching is not required for donor selection as per guidelines
• However, worth taking into consideration when multiple suitable donors are
available.
• Myeloablative conditioning, if feasible

33. Minor ABO mismatch

34. Minor ABO mismatch – 3 complications
• Acute haemolysis of recipient RBCs
• Donor-derived isohemagglutinins infused along with the stem cell products,
causing acute hemolysis of recipient RBCs.
• Passenger lymphocyte syndrome (PLS)

35. Passenger lymphocyte syndrome (PLS)
• Occurs when transplanted B lymphocytes produce incompatible
blood group antibodies after transplantation.
• Hemolysis associated with PLS is delayed 5 to 15 days post-
transplantation and is rare after 6 to 8 weeks.

36. Passenger lymphocyte syndrome (PLS)

37. Preventive strategies
• Graft plasma volume reduction
• Reduce risk of acute haemolysis
• Does not prevent PLS because it does not affect the B-cell
component in the graft.
• Maintaining higher Hb than the normal transfusion threshold
• Especially during the high-risk period
• To avoid nadir in case severe or life-threatening PLS occurs.

38. Transplantation time periods
• Phase 1 – Pre-transplantation
• Phase 2 – Transplantation until engraftment
• Phase 3 – Post engraftment
• Engraftment is defined as the first of 3 consecutive days with an
absolute neutrophil count higher than 0.5 × 109 /L (sustained >20 ×
109 /L platelets and hemoglobin >80 g/L, free of transfusion
requirements). (EBMT, 2019)

39. Transfusion support

40. Switching to Donor-type blood
• Only donor‐type red cells present (Without mixed field population)
• No transfusion for 90‐120 days (Varies with organisations)
• No incompatible isohemagglutinins against the new RBC phenotype
can be detected in 2 consecutive blood samples
• 100% donor type by molecular studies
• Negative DAT at the time of switch (Varies with organisations)

41. Back to the patient…

42. Recipient Anti-A titre (29/5/23)
• Blood group – O Rh(D) Positive
• RH Phenotype – Cde/Cde (R1 R1)
• Direct Coombs’ test – Negative
• Antibody screening - Negative
• Anti-A titre
• Anti-A IgM
• At Room temperature – 1:128
• At 4OC – 1:128
• Anti-A IgG
• At 37OC – 1:256
• At AHG phase – 1:128

43. Before DFPP (29/5/23)
• Anti-A IgM
• At 4OC – 1:128
• At Room temperature – 1:128
• Anti-A IgG
• At 37OC – 1:256
• At AHG phase – 1:128
After DFPP (15/6/23)
• Anti-A IgM
• At 4OC – 1:64
• At Room temperature – 1:64
• Anti-A IgG
• At 37OC – 1:16
• At AHG phase – 1:32
• Anti-B IgM
• At 4OC – 1:64
• At Room temperature – 1:32
• Anti-B IgG
• At 37OC – 1:32
• At AHG phase – 1:32
• Double filtration plasmapheresis (DFPP) on 9/6/23, 12/6/23, 13/6/23

44. Peri-transplant
• Complications
• Grade IV oral mucositis
• Neutropenic sepsis
• Transfusion needed
• Packed cells – 2 units (Blood group O)
• Apheresis Platelet – 3 units (Blood group A or AB)
• Engraftment
• WBC – Day +11
• Platelet – Day +14
• Discharged – Day +16

45. Conclusion
• ABO matching is not required for a successful HSCT
• HSCT across the barrier of RBC antigen mismatch may lead to acute
hemolysis, PLS, and PRCA
• Active collaboration between transfusion and transplantation services
might help with early identification of clinically significant antibodies
and prompt necessary treatment interventions.

46. Migdady Y, Pang Y, Kalsi SS, Childs R, Arai S. Post-hematopoietic stem cell transplantation immune-mediated
anemia: a literature review and novel therapeutics. Blood Adv. 2022;6(8):2707-2721.