HLA antibodies

These are antibodies to human leukocyte antigens, which are primarily IgG antibodies. In the context of transfusion medicine, these can be a cause of immune-mediated platelet refractoriness—a poor response to a platelet transfusion not caused by non-immune etiologies, such as disseminated intravascular coagulopathy, sepsis, splenic sequestration, or medications, to name a few.