PATHCHAT Edition No. 55
April 2019
Please contact your local Ampath pathologist for more information.
Author: Dr. Petri Swanepoel, MBChB (UP), MMed (Haem) (UP), FCPath (SA) (Haem)
Introduction
✅ HLA Typing and Screening at Ampath
- Ampath Immunology now offers HLA tissue typing and antibody screening using Luminex PCR-based multiplex technology.
- This platform ensures accurate, reliable, and standardized results with a faster turnaround time.
📌 Human leukocyte antigen (HLA) testing is critical in transplantation, disease association studies, and immune response research.
Introduction to HLA Molecules
✅ Major Histocompatibility Complex (MHC) Overview
- HLA genes are located on the short arm of chromosome 6.
- MHC encodes cell surface markers essential for immune system function.
- HLA molecules present proteins (self or non-self) to T-lymphocytes, influencing immune responses.
🔹 HLA Class I and Class II Molecules:
✔ Class I (Expressed on All Nucleated Cells & Platelets):
- HLA-A
- HLA-B
- HLA-C
✔ Class II (Expressed on Antigen-Presenting Cells):
- HLA-DR
- HLA-DQ
- HLA-DP
📌 HLA genes are highly polymorphic, leading to extensive diversity in populations.
HLA Typing: Indications & Methods
✅ Clinical Applications of HLA Typing:
- Transplant Medicine:
- Determines donor-recipient tissue compatibility.
- Prevents solid organ rejection and graft-versus-host disease (GVHD) in stem cell transplants.
- Disease Associations:
- Helps diagnose conditions linked to specific HLA alleles.
- Pharmacogenomics:
- Identifies genetic markers for drug hypersensitivity reactions (e.g., HLA-B*57:01 and Abacavir hypersensitivity).
- Immunotherapy & Vaccine Development:
- Used in cancer immunotherapy and vaccine research.
✅ Molecular vs. Serological HLA Typing:
✔ Serological Typing (Older Method, Limited Use):
- Uses antisera to detect specific HLA molecules.
- Low reproducibility and limited detection of rare antigens.
✔ Molecular Typing (Current Standard, High Accuracy):
- Uses PCR-based or DNA sequencing methods.
- Higher resolution and specificity.
- Better reproducibility and ability to detect rare alleles.
📌 Molecular HLA typing has replaced serological methods for improved accuracy and reliability.
HLA Nomenclature & Sample Collection
✅ HLA Naming System:
- More than 21,000 known HLA alleles.
- New alleles are assigned by the World Health Organization’s Nomenclature Committee for the HLA System.
- Full details available at: hla.alleles.org
✅ Sample Collection for HLA Typing:
- Collect 4 EDTA (purple top) or ACD (light yellow top) tubes.
- Samples accepted Monday to Friday.
📌 HLA testing requires high-quality DNA; ensure correct sample collection for accurate results.
HLA Antibody Screening
✅ Why Screen for HLA Antibodies?
- HLA antibodies can cause graft rejection in organ and stem cell transplantation.
- Donor-specific antibodies (DSA) are associated with poor graft survival.
- Identifying DSAs allows better immunological risk stratification and post-transplant monitoring.
✅ Luminex Technology – LabScreen Testing at Ampath
- Step 1: Screening test detects the presence of HLA Class I or Class II antibodies.
- Step 2: If positive, a detailed assay specifies the antibody at the allelic level.
📌 HLA antibody screening improves transplant success and long-term graft survival.
Post-Transplant Antibody Monitoring
✅ Importance of Post-Transplant Monitoring:
- Detects low-level or newly formed DSAs.
- DSAs may indicate early signs of chronic graft rejection before biochemical markers (e.g., creatinine in kidney transplants).
✅ Sample Collection for Post-Transplant Monitoring:
- Collect 1 SST tube (yellow top).
- Samples accepted Monday to Friday.
📌 Post-transplant antibody monitoring helps predict graft rejection and allows timely interventions.
HLA & Disease Associations
✅ HLA Typing in Autoimmune & Genetic Disorders:
- HLA-B*27 → Ankylosing spondylitis.
- **HLA-DRB103/04 → Type 1 diabetes mellitus.
- **HLA-DQ02/08 → Coeliac disease.
✅ HLA Typing in Drug Reactions:
- HLA-B*57:01 → Hypersensitivity to Abacavir (HIV treatment).
📌 HLA typing assists in diagnosing immune-mediated diseases and preventing severe drug reactions.
Contact Information for HLA Testing at Ampath
✅ For HLA Typing & Screening Queries:
- Ampath’s Cellular Immunology Laboratory: 012 678 0530
- Dr. Petri Swanepoel: 012 678 0613/4
📌 For more information on HLA testing, consult Ampath’s Immunology Department.
Key Takeaways for Clinicians
✅ HLA typing plays a critical role in transplant medicine, disease diagnosis, and pharmacogenomics.
✅ Molecular HLA typing using PCR-based methods is more accurate than serological methods.
✅ HLA antibody screening identifies donor-specific antibodies, improving transplant outcomes.
✅ Post-transplant antibody monitoring can predict graft rejection before clinical deterioration.
✅ HLA associations aid in diagnosing autoimmune diseases and identifying drug hypersensitivity risks.
📌 HLA typing and antibody screening are essential tools for precision medicine and transplant success.