Long-term evolution of lymphocytes subsets after induction therapy based on continuous versus discontinuous administration of anti-thymocyte globulins in renal-transplant patients

The aim of our retrospective study was to assess the long-term evolution of lymphocyte subsets after two modes of administration of anti-thymocyte globulin (ATG) after renal transplantation. Methods. Before 1993, patients (group I, n = 93) received fixed doses of RATG (1 mg/kg per day) for 8 consecutive days. Thereafter, RATG was either continued at the same dose for 15 days, in cases of delayed graft function, or was infused every other day at the same dose until the serum creatinine level became < 150 mu mol/L. After 1993, patients (group II, n = 66) received RATG at full dose (1 mg/kg per day) during the first 3 days and, thereafter, doses were adapted to target a CD2 T-cell count < 50/mm(3). RATG cumulative dose was significantly higher among group I than group II (9.7 +/- 4.5 versus 7.4 +/- 3.2 mg/kg, P =.0002). Results. In both groups, total lymphocyte and T lymphocyte subset (CD4, CD8, CD2, CD3) counts decreased significantly during the first month after transplantation, increasing slowly between the first month and the third year posttransplantation. Thereafter it rose rapidly, which was greater in group II. At last follow up, total lymphocyte, T lymphocyte subsets and NK cell counts were similar to those observed before transplantation. At all monitoring times, T lymphocyte, B lymphocyte, and NK cell counts were similar in both group, except for the total lymphocyte count at 6 months and CD4 T lymphocyte count at 1 year, which were significantly higher in group II compared to group I. Conclusion. Induction therapy based on continuous or discontinuous administration of ATG is associated with profound depletion of T, B, and NK cells during the first 3 years, followed by a progressive reconstitution of the lymphocyte pool after 5 years.