Donor A
10/10- Age
- 26
- Availability
- Confirmed
- Recipient DSA
- None detected
DPB1 · fictional lab reportPermissive mismatch
01 / READ THE MATCH
~1 minuteFind the match.
Two copies at each HLA gene. Tap a donor to compare their tissue type with the patient’s.
Your move: find an 8/8 match.
ALLELES MATCHED
7/8
HLAPatientDonor 01
Same allele Different allele ≠
This is a match count, not a chance of donation.
What do 8/8 and 10/10 mean?+
8/8: two allele copies at each of HLA-A, B, C and DRB1. 10/10: add the two DQB1 copies.
HLA proteins help the immune system recognize cells. HLA is different from ABO blood type. The match count does not measure survival, graft success or the chance you will be selected.
An allele is a version of a gene. The shorthand 02:01 in row A means HLA-A*02:01. Order within a pair does not matter.
The fictional profiles use simplified two-field notation. Clinical laboratories also resolve typing ambiguities, expression and antigen-recognition-domain equivalence. These tiles are not a clinical typing tool.
02 / THINK LIKE THE TRANSPLANT TEAM
2 short casesSame count.
Different clues.
The goal is good reasoning. There is no universal “best donor” score.
FICTIONAL CASE A
An adult with AML is being evaluated for transplant. Two unrelated donors have the same 10/10 count, age and availability.
Donor B
10/10- Age
- 26
- Availability
- Confirmed
- Recipient DSA
- None detected
DPB1 · fictional lab reportNonpermissive mismatch
GVHD: graft-versus-host disease. PTCy: cyclophosphamide given after transplantation. CNI: calcineurin inhibitor. A PTCy regimen may also include a CNI.
What is a permissive mismatch?+
Some DPB1 mismatches have a more favorable immune-risk pattern than others in conventional transplant settings. T-cell-epitope (TCE) models help classify them.
“Permissive” does not mean identical or risk-free. It is not something you can read from the numerical closeness of allele labels. The labels in this case are preassigned fictional laboratory interpretations.
DPB1 is kept separate here: adding it to make a “12/12” target would hide the role of the prevention regimen. Evidence about specific mismatches under PTCy continues to evolve.
FICTIONAL CASE B · PTCy PLANNED
An adult with AML needs a timely transplant. These are the initial search findings, not medically cleared donors.
Donor C
8/8- Age
- 25
- Availability
- Unconfirmed
- Recipient DSA
- Pending
Donor D
7/8- Age
- 24
- Availability
- Confirmed
- Recipient DSA
- Pending
The antibody clue+
Donor-specific antibodies (DSAs) are recipient antibodies directed against a donor’s HLA. They can threaten engraftment. A negative screen cannot be assumed from an 8/8 count; other HLA loci can still differ.
Identify antibody specificity and avoid a donor carrying a targeted mismatch when possible. Assessment and any management belong to the transplant and histocompatibility teams. In these two profiles, “pending” means this question is still unanswered.
03 / UNDERSTAND THE ODDS
Math sandboxMore people.
More possibilities.
How does a larger pool change the chance of finding at least one HLA match?
Hypothetical modelThese are invented match rates, not clinical estimates.
010,000
MODEL CHANCE OF ≥1 HLA MATCH63.2%In hypothetical searches of 1,000 donors.
100 hypothetical patient searches
Each dot is a patient search, not a donor. Re-running can give different results.
Show the math & assumptions+
P(at least one match) = 1 − (1 − p)n
p is an assumed match probability for one donor; n is the number searched. The model assumes independent donors with the same fixed probability, complete typing and no existing match. It models HLA matching only.
Real searches depend on the patient’s HLA, the population sampled and who is represented in the registry. HLA alleles are inherited in linked groups; you cannot multiply independent “tile match” odds to estimate a real match rate.
Contactability, consent, medical suitability, selection and timing are additional questions. This model does not estimate them. It cannot predict Dave’s match, any particular person’s chance of donating, or transplant outcomes.
THREE DIFFERENT QUESTIONS
Does this donor match this patient?Answer with HLA typing.
Will this registrant ever donate?No reliable individual percentage is supplied here.
Will a patient find a suitable donor?Requires a patient-specific search and clinical review.
04 / FOLLOW THE DONOR
One step at a timeA swab is
the beginning.
Explore the route to donation. Every step has its own question.
Not selected?
Remain available if eligible and willing. A match may never lead to donation.
What does donation look like?+
Among people who donate through NMDP, approximately 90% give peripheral blood stem cells (PBSC) and 10% give marrow.
PBSC collection uses apheresis after medication mobilizes stem cells. Marrow collection uses needles in the back of the pelvic bones under anesthesia.
The patient’s doctor requests the method; the donor gives informed consent. These proportions do not describe your probability of being selected.