Graft versus host disease The occurrence of GVHD is influenced by many well known factors. Although the use of nonmyeloablative SCT can reduce the severity of GVHD, GVHD remains a major complication. In our pilot study using the reduced intensity preparative regimen in RC, the probability for developing GVHD grade IIIV was 0.48. It is accepted that in comparison to myeloablative SCT, in reduced intensity preparative regimens higher proportions of host immune hematopoietic cells may persist. While donor-derived alloreactive lymphocytes are being infused, these autologous cells might possibly serve as host antigen presentation for continuous stimulation of donor T-cells. Consequently, it was speculated by the group Shapira and Slavin10 that GVHD may be similarly amplified by reduced conditioning followed by intentional administration of host cells. This hypothesis was tested in a preclinical animal model. Increased incidence of GVHD, higher mortality and increased levels of chimerism were observed in recipients reconstituted with additional host cells, particularly with non-irradiated spleen cells. Graft-versus-Leukaemia (GVL) effect was not impaired by post transplant cell administration. These results suggested that GVHD may be amplified by recipient cell infusion using either irradiated or viable stimulatory host cells. This could possibly explain the higher than anticipated incidence of GVHD and consequently the rapid displacement of host cells with conversion to 100% donor type cells in reduced intensity SCT. The present study will therefore investigate whether autologous antigen presenting cells (Auto-APC) do survive the conditioning regimen and favour to occurrence of GVHD.