Medical Laboratory Scientist ASCP Practice Exam 2025 – Complete Study Guide

Hypersensitivity reactions during blood transfusions primarily involve the antibody type IgM. IgM is the first antibody produced in response to an antigen and is particularly effective in agglutinating and lysing foreign blood cells. In the context of a blood transfusion, if a patient receives blood containing an antigen that their body recognizes as foreign (for example, mismatched ABO blood types), IgM antibodies are quickly activated. These antibodies can bind to the antigens on the transfused red blood cells, leading to their destruction through agglutination and complement activation, which can result in acute hemolytic transfusion reactions.

While IgG antibodies can also play a role in transfusion reactions, especially in cases of delayed hemolytic reactions, it is primarily IgM that is responsible for the immediate and acute responses typically associated with improper blood transfusions.

Other antibodies such as IgE and IgA are less involved in this specific hypersensitivity reaction. IgE is primarily associated with allergic responses and parasitic infections, while IgA is more commonly found in mucosal sites and does not play a significant role in blood transfusion reactions. Understanding the role of IgM helps clarify the immediate immune response that can lead to serious complications during transfusions