Which of the following is NOT associated with the major histocompatibility complex?

The major histocompatibility complex (MHC) plays a critical role in the immune system by presenting peptide antigens to T cells, which is essential for the immune response, particularly in organ transplantation, autoimmune diseases, and paternity testing.

In organ transplantation, the compatibility of donor and recipient MHC molecules is a key factor in the acceptance or rejection of transplanted tissues. Mismatches can trigger an immune response against the transplanted organ.

For paternity testing, MHC molecules can be analyzed to determine the genetic relationships between individuals, as certain MHC alleles are inherited and can be present in both parents and offspring.

Autoimmune diseases often involve the MHC because specific alleles can predispose individuals to these conditions. The way these molecules interact with the immune system can lead to self-tolerance breakdown, resulting in an autoimmune response.

Acute hemolytic transfusion reactions are primarily associated with blood group antigens, particularly ABO and Rh factor, rather than MHC. In these cases, transfusion reactions occur due to the incompatibility of red blood cell antigens between donor and recipient, leading to destruction of the transfused blood cells. This illustrates why acute hemolytic transfusion reactions do not hinge on the roles of M