Prolonged survival of xenografts after organ culture.

Recent reports demonstrate that culture of thyroid allografts before transplantation results in prolonged and sometimes indefinite survival. The loss of passenger leukocytes during organ culture was discussed as a possible reason for these findings. Recent data from a genetically defined system in the mouse demonstrated that passenger leukocytes play an important role in providing a helper stimulus which potentiates the generation of cytotoxic T cells to serologically defined determinants. To ascertain whether this mechanism also is involved in a xenogeneic system, cultured Wistar thyroids were transplanted to DBA/2 mice. The experimental system used was described first by Lafferty and co-workers. Thyroid function was determined by 125-iodine uptake of the graft and by histology. Fresh Wistar thyroids were rejected after a short period of good function on the sixth day after transplantation. Culturing for 10 days resulted in a prolonged graft function up to the fifteenth day. However, if the thyroids were kept in culture for 27 days, no functional signs of rejection could be detected on the twenty-fifth day after transplantation by iodine uptake. The iodine uptake ratio was 47.1 (control group on day 6 was 2.4). Injection of 10(5) fresh donor cells at the time of transplantation reversed the effect of long-term organ culture.