[The immunosuppressive effect of cholera toxin on rat renal allograft]

Immunomodulatory effects of cholera toxin (CT) were investigated in a rat model, and the effects of CT on rat renal allograft (from Lewis rat to WKAH rat) were also examined. The results are: 1) The number of lymphocytes in the thymus, spleen and peripheral blood was remarkably decreased after 7 day administration of CT (0.1 and 0.2 mg/kg/day), but the number of red blood cells and neutrophils was not decreased. 2) CT suppressed mixed lymphocyte reaction (MLR) in a dose dependent fashion, and % suppression reached 97% at the concentration of 10 micrograms/ml. The later the time of addition of CT to MLR, the less became this effect. 3) In the control group, the mean survival time (MST) after transplantation was 8.5 +/- 0.3 (Mean +/- SE) days. CT, given 1 day before transplantation, did not prolong MST. In the group to which CT was given daily for 14 days from the day of transplantation, MST was prolonged with the increase of CT. CT at the dosage of 0.2 mg/kg/day prolonged MST (16.2 +/- 3.2 days) significantly (p less than 0.05), where treated with CT from the 3rd day after transplantation, MST (10.3 +/- 1.3 days) was not significantly prolonged. From the above findings, CT seems to act mainly on the early phase of acute rejection and prolongs rat renal allograft survival.