Cord Blood HLA Matching and Compatibility 2 — Questions and Answers
Question 1: Which HLA loci are considered the MOST critical in cord blood unit selection?
- HLA-A, B, and C only
- HLA-DR and DQ only
- HLA-A, B, and DRB1 (Correct answer)
- HLA-DP and DQ only
Correct answer: HLA-A, B, and DRB1
HLA-A, B, and DRB1 are the most critical loci for cord blood matching and form the traditional core of the 6/6 matching framework.
Question 2: Which HLA typing method provides the highest resolution and most precise matching data?
- Serology-based typing
- Low-resolution molecular typing
- High-resolution allele-level molecular typing (Correct answer)
- Flow cytometry-based typing
Correct answer: High-resolution allele-level molecular typing
High-resolution allele-level molecular (DNA-based) typing provides the most precise HLA matching data and is the current standard for transplant selection.
Question 3: A cord blood unit described as a 5/6 HLA match has a mismatch at which level?
- Two alleles at two different loci
- One allele at one locus (Correct answer)
- Three alleles across three loci
- All alleles at one complete locus
Correct answer: One allele at one locus
A 5/6 match means five of six typed HLA alleles match between donor and recipient, with a mismatch at one allele.
Question 4: What does 'bidirectional HLA typing' evaluate in cord blood transplantation?
- Testing both donor and recipient HLA in the same laboratory
- Assessing mismatches in both the graft-versus-host and host-versus-graft directions (Correct answer)
- Matching one cord blood unit to two recipients simultaneously
- Performing HLA typing at two separate facilities for confirmation
Correct answer: Assessing mismatches in both the graft-versus-host and host-versus-graft directions
Bidirectional HLA typing evaluates mismatches in both directions — graft-versus-host (GvHD risk) and host-versus-graft (rejection risk) — to comprehensively assess compatibility.
Question 5: How does a higher total nucleated cell (TNC) dose in a cord blood unit influence acceptable HLA mismatch levels?
- Higher TNC dose allows greater HLA mismatches to be accepted (Correct answer)
- Higher TNC dose requires stricter HLA matching
- TNC dose has no relationship to acceptable HLA mismatch
- HLA mismatch and TNC dose are evaluated on entirely separate criteria
Correct answer: Higher TNC dose allows greater HLA mismatches to be accepted
Higher TNC dose can partially compensate for greater HLA mismatch because more cells improve the probability of successful engraftment despite immunological barriers.
Question 6: What are cross-reactive groups (CREGs) in the context of HLA matching?
- HLA antigens that trigger the strongest immune reactions
- Clusters of HLA antigens sharing structural epitopes that may be immunologically cross-reactive (Correct answer)
- Groups of patients who react to the same cord blood units
- HLA alleles found only in certain ethnic populations
Correct answer: Clusters of HLA antigens sharing structural epitopes that may be immunologically cross-reactive
CREGs are clusters of HLA antigens that share common epitopes and may be serologically cross-reactive, sometimes considered acceptable mismatches in transplantation.
Question 7: What is a 'permissive' HLA mismatch in cord blood transplantation?
- Any mismatch occurring at the HLA-C locus
- A mismatch associated with acceptable clinical outcomes based on evidence (Correct answer)
- A mismatch between HLA class I and class II antigens
- A mismatch involving only rare HLA alleles
Correct answer: A mismatch associated with acceptable clinical outcomes based on evidence
A permissive mismatch is one that clinical data suggests does not significantly worsen transplant outcomes and is therefore acceptable in unit selection.
Cord Blood HLA Matching and Compatibility 2
Which HLA loci are considered the MOST critical in cord blood unit selection?