INCREASED REJECTION OF MURINE ALLOGENEIC BONE-MARROW IN PRESENSITIZEDRECIPIENTS

The role of presensitizing murine recipients with donor spleen cells p rior to T cell-depleted or -repleted H-2 compatible allogeneic bone ma rrow transplantation (BMT) was investigated at two different doses of total body irradiation (TBI). Recipients that were presensitized with 2 x 10(7) irradiated donor spleen cells at 1 week before a sublethal d ose of 6 Gy TBI and BMT showed no evidence of donor blood chimerism wh ile unsensitized recipients showed about 80% donor engraftment as dete rmined by blood Gpi phenotyping. After raising the TBI dose to 9.5 Gy an increase in mortality from marrow failure was observed in presensit ized animals. No significant engraftment-promoting effect of up to 2 x 10(6) T cells (20% of total marrow dose) was seen either in presensit ized or unsensitized mice. It can be concluded that presensitized reci pients are more susceptible to acute marrow rejection and that T cells added to the bone marrow did not influence the level of donor engraft ment in these recipients.