Dosage of FK506 and infiltrating lymphocytes in small bowel transplanted rat

We studied optimal dosage of FK506 and the mechanism of immunosuppression as well as the formation of chimerism based on infiltrating lymphocytes. Afer small bowel transplantation in Brown Norway x Lewis rats, no rejection was observed using at 0.2mg/kg/day of FK506 for 2 weeks, but temporary graft versus host disease (GVHD) was observed. An administration of 0.5mg/kg/day of FK506 for 2 weeks induced neither GVHD nor host versus graft disease (HVGD) in rats and they survived for over 150 days. Analysis of lymphocyte subsets showed that CD25 (IL-2 receptor) and CD8 (Cytotoxic T Lymphocyte) of graft were suppressed by FK506. The mechanism of immunosuppression with long-term survived models may be suppressed function of CD8 positive cells by FK506. But, further T cell function analysis is needed to clarify these finding. Immunohistochemical staining of infiltrating lymphocytes with long-term survived models proved the formation of chimerism.