What causes hyperacute transplant rejection?

Hyperacute transplant rejection is primarily caused by the presence of preformed antibodies against donor human leukocyte antigens (HLA) and ABO blood group antigens. This type of rejection occurs almost immediately after the transplantation, often within minutes or hours, due to an existing immune response.

When a transplant is introduced into the recipient's body, if preformed antibodies that react against the donor's antigenic structures are present, they will immediately bind to these antigens. This binding activates the complement system and leads to a rapid inflammatory response, resulting in thrombosis and subsequent necrosis of the graft tissue. The speed of this rejection process is due to the recognition by the host immune system of the foreign antigens, which have already stimulated the production of antibodies prior to the transplantation, perhaps from a previous transplant, blood transfusion, or pregnancy.

In contrast, delayed hypersensitivity, cell-mediated immunity, and chronic inflammation are mechanisms associated with other forms of rejection, such as acute and chronic rejection. These processes involve T-cell mediated responses and take longer to develop, typically manifesting days or weeks post-transplant rather than instantly. Understanding the mechanisms behind hyperacute rejection is crucial for transplant immunology and highlights the need for careful matching of donor and recipient profiles to prevent