A doctoral scientist and his research group at a blood center in Toronto have found, in studies of T cell-antigen specific responses, that doses of irradiation up to 10 Gy may be required with the blood of some donors in order to prevent activation and proliferation of leukocytes in vitro. With this in mind he questions the use of a standard irradiation dose of 2.5 Gy to prevent graft-versus-host disease in transfusion recipients. The Toronto scientist is curious to learn how transfusion services assure that the irradiation dose that they deliver to blood products actually prevents clonal expansion of TA-GVHD causing leukocytes, particularly from one donor to the next and using only one dose of irradiation, such as 2.5 Gy. What is the experience of the blood banking community?

The following reponses have been received.

ADDENDA Sept. 23, 2003

1. A colleague is concerned with the statement of the Toronto scientist that a standard irradiation dose of 2.5 Gy is used to prevent GVHD following the transfusion of cellular blood products, because the 22nd edition of the AABB Standards states in 5.7.4.2 that "The intended dose of irradiation shall be a minimum of 25 Gy (2500 cGy) delivered to the central portion of the container. The minimum dose at any point in the components shall be 15 Gy (1500 cGy). If the Toronto scientist's data are measuring the effects of 2.5 Gy - 10 Gy irradiation on blood products, it would not be surprising that his data suggest that 2.5 Gy - 10 Gy may not be sufficient to surpress clonal proliferation in every individual instance.

ADDENDA Sept. 25, 2003

2. A transfusion medicine physician in Sacramento reports that at his regional blood center the amount of radiation given to blood components to prevent activation and proliferation of T-cells is 30 Gy to make sure all parts of the bag receive a sufficient dose. He correctly points out that per AABB Standards, the minimum dose is 25 Gy to the midplane and at least 15 Gy to all parts of the component.

ADDENDA Sept. 26, 2003

3. A transfusion medicine physician in India reports that their hospital is currently looking at the issue of validation of a blood irradiator now. Their dosimetry studies have shown adequate radiation delivery, but the actual effect on the lymphocytes have yet to be validated. They are looking at the possibility of doing lymphocyte blast transformation studies, and want to know if others have suggestions for this validation.

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Ira A. Shulman, MD
CBBS e-Network Forum Editor & Moderator