HLA/HPA compatible platelets

HLA compatible platelets

Human leucocyte antigens (HLA) are polymorphisms in cell surface molecules that distinguish 'self' from 'non-self'. They may also be involved in the pathogenesis of certain autoimmune and infectious diseases.

HLA compatible platelets may be required in patients who are at risk of developing or have developed antibodies to HLA antigens. HLA antibody development can occur due to prior exposure from transfusion, pregnancy, or transplant. These antibodies can cause failure to achieve satisfactory responses in platelet transfusion, that is platelet refractoriness. Platelet refractoriness is most commonly due to non-immune factors (like sepsis and splenomegaly), but in 20% of cases it is due to HLA antibodies. 

HLA-compatible platelets can be supplied at the direction of a Lifeblood Transfusion Medicine Specialist. 

Clinical indications:

• Patients who are refractory to random platelet transfusions due to the presence of HLA alloimmunisation. See Platelet disorders for more information on platelet refractoriness.
• Patients for whom a clinical decision has been made to proceed to haemopoietic stem cell transplantation (HSCT) using a donor who is not a full HLA match (i.e. a mismatched or haplo‑identical donor) and where the donor has been identified, and their mismatched HLA type is available. For these patients:
  • HLA compatible platelet support can be provided prior to transplant until the day of their stem cell infusion (day 0), irrespective of their HLA antibody status.
  • After day 0 of transplant, non-alloimmunised patients needing platelet transfusion can revert to standard non-matched pooled or apheresis platelet support.
  • Patients who are HLA alloimmunised (cPRA > 20%) and platelet refractory will continue to be supported with HLA compatible platelets after day of transplant.
• Congenital platelet function disorders such as:
  • Bernard-Soulier syndrome
  • Glanzmann Thrombasthenia
  • Other confirmed severe inherited platelet dysfunction disorders with a demonstrated bleeding phenotype where development of HLA alloantibodies may make future platelet support very difficult.

HPA compatible platelets

Human platelet antigens (HPA) are polymorphisms in platelet membrane glycoproteins that can stimulate production of alloantibodies once exposed to foreign platelets with different HPAs. HPA can also be targeted by autoantibodies and drug-dependent antibodies.

HPA alloantibodies are responsible for the following clinical conditions:

• fetomaternal and neonatal alloimmune thrombocytopenia (FNAIT/NAIT)
• post-transfusion purpura, and
• refractoriness to platelet transfusions.

HPA compatible platelets are supplied at the direction of a Lifeblood Transfusion Medicine Specialist