Reduction of fatal graft-versus-host disease by 3H-thymidine suicide of donor cells cultured with host cells.

The effect of the tritiated thymidine (3H-TdR) suicide technique on the ability of donor cells to induce fatal graft-versus-host disease (GVHD) was studied. C57BL/6 (H-2b) spleen cells were stimulated in vitro with irradiated BALB/c (H-2d) Moloney lymphoma cells in mixed culture and 3H-TdR of high-specific activity added to eliminate proliferating cells. The ability of such cells to induce fatal GVHD was assayed by injecting them i.v. into adult BALB/c mice immunosuppressed with cyclophosphamide (180 mg/kg). These cells induced fatal GVHD in fewer mice (52 per cent) than did C57BL/6 cells cultures with BALB/C lymphoma cells but without 3H-TdR (87%) and C57BL/L cells cultured with irradiated C57BL/6 cells with (95 per cent) or without 3H-TdR (86 per cent). Thus, the 3H-TdR suicide technique greatly diminished the ability of cells to induce lethal GVHD.