Human Leukocyte Antigen (HLA) antibodies are antibodies directed against HLA Class I or Class II molecules. They are clinically significant in several contexts: 1) **Transplantation**: Pre-formed donor-specific HLA antibodies (DSA) can cause **hyperacute or acute antibody-mediated rejection** of solid organ transplants. Patients awaiting transplant are screened for HLA antibodies via a **panel reactive antibody (PRA)** test. 2) **Platelet Transfusion Refractoriness**: HLA antibodies are the most common cause of immune-mediated platelet refractoriness. 3) **Transfusion-Related Acute Lung Injury (TRALI)**: Donor HLA antibodies (usually from multiparous female donors) reacting with recipient leukocytes are a leading cause of TRALI. 4) **Neonatal Alloimmune Neutropenia**. HLA antibodies are **not** typically involved in classic hemolytic transfusion reactions (those are against RBC antigens). They are commonly formed after **pregnancy, transfusion, or transplant** due to exposure to foreign HLA antigens.

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Zambia

• loveness Phiri – 801 pts

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