[Transfusion-associated graft-versus-host disease guideline on gamma irradiation of blood components]

Transfusion-associated graft-versus-host disease (TA-GVHD) is a rare and usually fatal syndrome. Clinical manifestations are fever, maculopapular skin rash, nausea, vomiting, diarrhea, hepatitis and pancytopenia owing to bone marrow hypoplasia. It can occur in recipients with severe immunosuppression and in immunocompetent recipients after transfusion of cellular components from HLA homozygous donor to recipients heterozygous for that HLA haplotype. The diagnosis is made by clinical manifestation and skin biopsy. Antithymocyte globulin and high dose systemic corticosteroids are both the most used therapy. The back of knowledge about this syndrome, the rapid evolution and the absence of treatment response are related to patients bad evolution. Gamma irradiation of blood products has been the mainstay of TA-GVHD prevention. Dose of 2500 cGy is required to completely inactivate T cells. Irradiation damage red cells membrane and the red celis units can not be storage for long time after irradiation. High potassium levels is the mainly change in red cells units. White cell-reduction filters do not prevent TA-GVHD and gamma irradiation does not prevent alloimmunization or blood reactions. Only cellular components like whole blood, red cells, platelets and granulocytes need be irradiated. Ali blood components should be irradiated to: first or second-degree relatives, patients need HLA-matched platelets, recipients of allogeneic or autologous bone marrow transplantation, patients with Hodgkin's disease, patients treated with purine analogue drugs, intrauterine transfusion, pre-term infants and when congenítal immunodeficiency states is suspected. It is recommended irrradiated blood to patients with neoplastic disease when they receive intensive chemotherapy.