BACKGROUND: Tacrolimus (FK506) is an immunosuppressive agent used in clinical transplantation. We studied the acute impact of FK506 on T-lymphocyte populations of peripheral blood and spleen in rats. METHODS: The animals injected with FK506 (2 mg/kg) subcutaneously were sacrificed at 12, 24, or 48 hours after administration. CD3(+), CD4(+) and CD8(+) T-cell populations in peripheral blood and spleen were analyzed by FACS. RESULTS: After treatment with FK506, the proportion of CD4(+) cells significantly increased in the spleen at 12 hours, decreasing to control levels at 24 and 48 hours. There was a slight increase in the CD4(+) subpopulation in the peripheral blood at 12 and 24 hours and a significant increase at 48 hours. The CD8(+) T-cell subpopulations in peripheral blood and spleen were stable during FK506 administration. CONCLUSIONS: These results indicated that FK506 increased CD4(+) spleen lymphocyte activation in a short time, inducing a subsequent increase in CD4(+) cells subsets in peripheral blood.
BACKGROUND:Tacrolimus (FK506) is an immunosuppressive agent used in clinical transplantation. We studied the acute impact of FK506 on T-lymphocyte populations of peripheral blood and spleen in rats. METHODS: The animals injected with FK506 (2 mg/kg) subcutaneously were sacrificed at 12, 24, or 48 hours after administration. CD3(+), CD4(+) and CD8(+) T-cell populations in peripheral blood and spleen were analyzed by FACS. RESULTS: After treatment with FK506, the proportion of CD4(+) cells significantly increased in the spleen at 12 hours, decreasing to control levels at 24 and 48 hours. There was a slight increase in the CD4(+) subpopulation in the peripheral blood at 12 and 24 hours and a significant increase at 48 hours. The CD8(+) T-cell subpopulations in peripheral blood and spleen were stable during FK506 administration. CONCLUSIONS: These results indicated that FK506 increased CD4(+) spleen lymphocyte activation in a short time, inducing a subsequent increase in CD4(+) cells subsets in peripheral blood.