Graft versus Host disease is seen exclusively in immunocompromised patients where cellular blood products containing lymphocytes are given. These lymphocytes can mount an immune response against the compromised recipient. Irradiation of transfusions can be utilized to inactivate the lymphocytes prior to transfusion. Post-transfusion purpura is common with the development of platelet antibodies. The external purpura signal a reaction that may lead to profound thrombocytopenia which usually occurs about one week post transfusion.
Plasmapheresis is the recommended treatment.
Immune suppression is a debatable complication. The transfusion of leukocyte-containing blood products appears to be immunosuppressive causing a decrease in Natural Killer cell function, decreased phagocytosis and decreased helper to suppressor cell ratios. The reason for this is unclear. The effect was first seen in renal transplant patients in whom preoperative blood transfusions appeared to improve graft survival. The clinical significance of this effect on such things as cancer recurrence and post-operative infection is still unclear.