Pathophysiology of Alloimmunization From Transfusions?
Allogeneic blood transfusion is a form of temporary transplantation. This procedure introduces a multitude of foreign antigens and living cells into the recipient that persist for a variable time. A recipient who is immunocompetent may mount an immune response to the donor antigens (ie, alloimmunization), resulting in various clinical consequences, depending on the blood cells and specific antigens involved. The antigens most commonly involved can be classified into the following categories: (1) human leukocyte antigens (HLAs), class I shared by platelets and leukocytes and class II present on some leukocytes; (2) granulocyte-specific antigens; (3) platelet-specific antigens (human platelet antigens [HPAs]); and (4) RBC-specific antigens.
@mishtu The immunologic mechanism for alloimmunization to antigens present in transfused cells involves presentation of the donor antigens by donor antigen–presenting cells (APCs), ie, monocytes, macrophages, dendritic cells, B cells, to recipient T cells. Recognition of the MHC class II alloantigens by CD4+ recipient T cells and their subsequent activation requires a co-stimulatory signal from either the donor or recipient APCs. The TH 2 subset of CD4+ T helper cells secretes interleukin (IL)–4, IL-5, IL-6, and IL-10, which activates B cells and initiates the antibody response.
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