TY - CHAP M1 - Book, Section TI - Human Leukocyte and Platelet Antigens A1 - Coppage, Myra A1 - Stroncek, David A1 - McFarland, Janice A1 - Blumberg, Neil A2 - Kaushansky, Kenneth A2 - Lichtman, Marshall A. A2 - Prchal, Josef T. A2 - Levi, Marcel M. A2 - Press, Oliver W. A2 - Burns, Linda J. A2 - Caligiuri, Michael Y1 - 2015 N1 - T2 - Williams Hematology, 9e AB - SUMMARYThe human leukocyte antigens (HLAs) are highly polymorphic glycoproteins encoded by the major histocompatibility complex on chromosome 6. Their biologic function is presentation of antigenic peptides to T lymphocytes, and there are two major classes: class I (A, B, and C loci) and class II (DR, DQ, and DP loci). Class I antigens are present on almost all nucleated cells, whereas class II antigens are primarily expressed on B cells and other antigen-presenting cells such as dendritic cells, endothelial cells, and monocytes. These antigens play key roles in hematopoietic cell transplantation acceptance/rejection and allosensitization to nonleukoreduced blood transfusions leading to platelet transfusion refractoriness, with lesser, but distinct roles in solid-organ transplantation. Other clinically important lineage-specific white cell antigens include those on neutrophils, which are much less polymorphic and less commonly a cause of clinical problems than the HLA system. Antibody to neutrophil antigens plays a role in autoimmune neutropenia, and reactions such as transfusion-related acute lung injury. Platelets also possess a relatively limited number of polymorphic antigens that are involved in clinical problems such as posttransfusion purpura and platelet transfusion refractoriness, and neonatal problems such as alloimmune thrombocytopenia. SN - PB - McGraw-Hill Education CY - New York, NY Y2 - 2024/03/29 UR - hemonc.mhmedical.com/content.aspx?aid=1121105801 ER -