Effect of in vitro X-irradiation on lymphocyte and granulocyte function

Granulocyte transfusions have been complicated by graft-versus-host disease (GVHD) in the recipients. This risk can be eliminated by irradiation of the cell product. The effect of in vitro irradiation on elements of lymphocyte and granulocyte function was therefore studied in order to determine the dose of irradiation which blocked lymphocyte function without affecting the function of granulocytes. Lymphocyte blast transformation after stimulation with mitogens was reduced by 90% after irradiation with 1500 rad and by 97% after 5 000 rad. The response to microbial agents and allogeneic cells was far more radio-sensitive, being completely abolished after irradiation with 1 000 and 500 rad, respectively. Mobility was the function of polymorphonuclear leucocytes (PMN) most affected by irradiation, being slightly but significantly reduced after irradiation with 10 000-20 000 rad. The bactericidal activity was reduced only after irradiation with 40 000 rad or more, while the hexose monophosphate shunt activity and the myeloperoxidase activity were largely unaffected by irradiation with doses of up to 120 000 rad. Hence the results indicate that the irradiation of leucocytes intended for transfusion with a dose of 2 000 rad is likely to prevent GVHD without causing any apparent damage to the PMN.