What type of transfusion reaction is most likely to occur if the recipient's blood type is not matched with the donor's blood type?

A hemolytic transfusion reaction is the most likely type to occur when the recipient's blood type does not match the donor's blood type. This reaction happens because the recipient's immune system recognizes the foreign red blood cells from the donor as an invader and mounts an immune response against them. This is especially true in cases of ABO incompatibility, where the presence of antibodies against the donor blood type leads to the destruction (hemolysis) of the transfused red blood cells.

In hemolytic reactions, symptoms can manifest quickly and may include fever, chills, back pain, dark urine, and signs of shock, which can make this type of reaction particularly dangerous. This stands in contrast to other types of transfusion reactions, which, while still serious, have different underlying mechanisms and are not directly influenced by blood type incompatibility in the same way.

For instance, hypotensive reactions can occur due to various factors such as dehydration or anxiety rather than an immune response to mismatched blood type. Allergic reactions are typically related to the recipient's reaction to proteins in the donor blood, while febrile reactions usually arise from the recipient's response to white blood cells or platelets in the transfused blood, not specifically due to blood type