What is the least likely Human Leukocyte Antigen (HLA) phenotype for the next sibling in a family with known HLA phenotypes of the parents and children?

Medical Advisory BoardAll articles are reviewed for accuracy by our Medical Advisory Board
Educational purpose only • Exercise caution as content is pending human review
Article Review Status
Submitted
Under Review
Approved

Last updated: August 17, 2025 • View editorial policy

Personalize

Help us tailor your experience

Which best describes you? Your choice helps us use language that's most understandable for you.

Determining the Least Likely HLA Phenotype for a Sibling

The HLA phenotype B (A 03,24; B 40,44; C 07,08) is the LEAST likely phenotype for the next sibling in this family.

Analysis of HLA Inheritance Patterns

HLA genes are inherited as haplotypes - one complete set from each parent. To determine the least likely phenotype for the next sibling, we need to first identify the parental haplotypes.

Mother's HLA Phenotype:

  • A 03,29
  • B 07,44
  • C 07,16

Child 1's HLA Phenotype:

  • A 02,29
  • B 14,44
  • C 08,16

Child 2's HLA Phenotype:

  • A 24,29
  • B 40,44
  • C 03,16

Deducing Parental Haplotypes

From these phenotypes, we can deduce:

  1. Mother's Haplotypes:

    • Haplotype 1: A 29, B 44, C 16
    • Haplotype 2: A 03, B 07, C 07

  2. Father's Haplotypes (deduced from children):

    • Haplotype 1: A 02, B 14, C 08 (passed to Child 1)
    • Haplotype 2: A 24, B 40, C 03 (passed to Child 2)

Possible Sibling Phenotypes

With these parental haplotypes, the possible combinations for a sibling would be:

  1. Mother's Haplotype 1 + Father's Haplotype 1:

    • A 29,02; B 44,14; C 16,08

  2. Mother's Haplotype 1 + Father's Haplotype 2:

    • A 29,24; B 44,40; C 16,03

  3. Mother's Haplotype 2 + Father's Haplotype 1:

    • A 03,02; B 07,14; C 07,08

  4. Mother's Haplotype 2 + Father's Haplotype 2:

    • A 03,24; B 07,40; C 07,03

Evaluation of Given Options

Looking at the options provided:

A. A 24,29; B 40,44; C 03,16

  • This matches combination #2 above (Mother's Haplotype 1 + Father's Haplotype 2)

B. A 03,24; B 40,44; C 07,08

  • This does NOT match any possible combination
  • The B 44 would have to come with C 16 from the mother
  • The B 40 would have to come with C 03 from the father

C. A 02,29; B 14,44; C 08,16

  • This matches combination #1 above (Mother's Haplotype 1 + Father's Haplotype 1)

D. A 02,03; B 07,14; C 07,08

  • This matches combination #3 above (Mother's Haplotype 2 + Father's Haplotype 1)

E. A 03,24; B 07,40; C 03,07

  • This matches combination #4 above (Mother's Haplotype 2 + Father's Haplotype 2)

Conclusion

Option B (A 03,24; B 40,44; C 07,08) is the LEAST likely phenotype because it violates the principle of HLA inheritance as haplotypes. The specific combination of alleles in option B cannot be inherited from the deduced parental haplotypes.

Key Points to Remember:

  • HLA genes are inherited as complete haplotypes from each parent
  • Recombination between HLA loci is rare due to their close proximity on chromosome 6
  • When analyzing HLA inheritance patterns, tracking the complete haplotype is essential
  • The HLA-A, B, and C loci are closely linked and generally inherited together

This analysis demonstrates the importance of understanding HLA haplotype inheritance in predicting possible HLA phenotypes in siblings, which has significant implications for transplantation medicine and donor selection 1.

References

1
Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Related Questions

What is the probability of a sibling and daughter being a viable match for a stem cell transplant?
Are Human Leukocyte Antigens (HLAs) the genes that determine which antigens the immune system detects?
How do you find a match for a bone marrow transplant?
What are Human Leukocyte Antigen (HLA) variants?
What is the arrangement of the fibers of the annulus fibrosus (outer layer of the intervertebral disc) in the intervertebral disc?
In which scenario would you recommend irradiated blood components to prevent TA-GVHD in solid organ transplant patients using purine analogues for chemotherapy?
When is testing for elevated high sensitivity C-Reactive Protein (hs-CRP) considered in patients with risk factors for cardiovascular disease?
What is the difference between high sensitivity C-Reactive Protein (CRP) and C-Reactive Protein (CRP)?
Which collagen type is primarily involved in the annulus fibrosus of the intervertebral disc?
What is the recommended daily intake of vitamin B12 (cobalamin)?

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

Have a follow-up question?

Our Medical A.I. is used by practicing medical doctors at top research institutions around the world. Ask any follow up question and get world-class guideline-backed answers instantly.

Ask Question