Abstract
The NCI‐IBM continuous flow separator was adapted for use in untreated dog renal allotransplants. Studies in 39 dogs demonstrated that a 2‐hr period at 1000 rpm with regional heparinization and temporary femoral vessel cannulation would be tolerated. Follow‐up hematological studies demonstrated that during the 2‐hr treatment an average of 19.4 ± 10^9^ white cells were collected. These contained an average of 7.4 × 10^9^ lymphocytes. Red cells and platelet levels were not markedly affected in treated dogs. This leukopheresis treatment was then employed once in 14 untreated dog renal allotransplants either pretransplant, or at days 1–4 or 5–7 post‐transplant. Eight other renal allotransplants were splenectomized 2 weeks previously and similarly leukopheresed at one of the three treatment periods. Twelve untreated dog renal allografts survived 9.2 ± 0.2 days (± 1 se). Pretransplant leukopheresis dogs survived 7.8 ± 1.5 days. Dogs leukopheresed during 5–7 days post‐transplant survived 16.0 ± 2.7 days (p < 0.01). All splenectomized dogs leukopheresed pre‐ or post‐transplant had survival rates less than 12.8 ± 3.1 days. Fifteen azathioprine‐treated (5 mg/kg/IM) dog renal transplants lived 14.6 ± 0.67 days. Mechanical leukopheresis thus prolongs renal allograft survival, probably by suppressing lymphocyte levels. The effect is limited. Humoral factors are not affected. The leukopheresis effect is most beneficial at the fifth to seventh day after renal transplant, and it is not improved by prior splenectomy.