Human Leukocyte Antigen (HLA) Class I antigens (HLA-A and HLA-B) are expressed on the surface of platelets (though at lower density than on leukocytes). They are the primary target in **immune-mediated platelet transfusion refractoriness**. Patients who have been exposed to foreign HLA antigens through previous pregnancies, transfusions, or transplants can develop **anti-HLA antibodies**. When such a patient receives platelets from a donor whose platelets carry the corresponding HLA antigens, these antibodies bind to the donor platelets, leading to their rapid clearance by the reticuloendothelial system (primarily in the spleen). This results in a poor post-transfusion platelet count increment. To overcome HLA alloimmunization, **HLA-matched or HLA-compatible platelets** are provided. This involves selecting donors whose HLA type either matches the patient's or lacks the specific antigens against which the patient has antibodies. HLA matching is a key strategy for managing refractory patients.

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Zambia

• Joseph Soko – 101 pts

• Visual Pathway Lesions
• Positive and Negative Symptoms
• Hallucinations and Delusions
• Antipsychotic Medications
• Emergency: Environmental Emergencies