Humoral Rejection

Humoral or hyperacute rejection is an uncommon form of allograft iniury, primarily mediated by antibody and complement, occurring immediately or during the first week after transplantation. The antibodies are either preformed (anti-ABO) or represent antidonor antibodies that develop after transplantation.
During hyperacute rejection, the allograft becomes swollen and cyanotic and, depending on the severity, consumptive coagulopathy and operative site bleeding may develop.
The presence of preformed donor-reactive antibodies in the recipient before transplantation or of antidonor antibodies in a failed graft confirms the diagnosis. Decreased platelet counts and decreased total serum complement activity after transplantation are indirect signs of humorally mediated injury of the allograft.
From the histopathological point of view, platelet and fibrin thrombi are present in periportal sinusoids with neutrophilic exudation, red blood cell congestion and coagulative necrosis. Medium-sized arteries show endothelial hypertrophy, focal endothelial denudation and neutrophilic inflammation of the intima, occasional nonocclusive fibrin thrombi, medial thickening and medial myocyte pyknosis and vacuolization. Immunofluorescent findings include linear deposits of IgG or IgM with C1q, C3, C4 and fibrinogen in the arteries, veins and portal capillaries.