HLA class I-eluted platelets as an alternative to HLA-matched platelets

Area of Science:

• Hematology
• Immunology
• Transfusion Medicine

Background:

• Alloimmunized patients with refractory thrombocytopenia often require Human Leukocyte Antigen (HLA)-matched platelet transfusions.
• The high polymorphism of the HLA system limits the availability of suitable donors for all patients.
• Alternative strategies are needed to address HLA incompatibility in platelet transfusion therapy.

Observation:

• In vitro studies demonstrated that citric acid elution at pH 3.0 removes HLA antigens from platelets while preserving platelet-specific glycoproteins.
• This acid elution technique was adapted for clinical application, involving citric acid incubation and washing of random-donor platelet concentrates.
• Two alloimmunized patients received transfusions of these acid-treated platelets.

Findings:

• Platelet-specific glycoproteins remained unaffected by the acid elution process.
• HLA expression on platelets was generally reduced to below 25% of initial levels.
• One patient with a rare HLA type showed significant post-transfusion platelet increments (up to 47 x 10^9/L) and resolved bleeding after repeated transfusions with acid-treated platelets.
• No adverse effects were observed in this patient.
• A second patient experienced a severe transfusion reaction with no platelet increment after one transfusion of platelets with 30% residual HLA expression, and further transfusions were withheld.

Implications:

• The acid elution technique shows promise for HLA-eluted platelet preparation in transfusion therapy.
• Further standardization and clinical validation are required to establish the safety and efficacy of this method.
• HLA-eluted platelets may become a valuable option for patients with refractory thrombocytopenia due to HLA alloimmunization.