To explore whether the complete donor chimerism could be achieved and graft-versus-host disease could be alleviated by donor lymphocyte infusion which was sensitized by the skin of the recipient, female C57BL/6 mice (H-2(b), B6) as recipients received total body irradiation (TBI) of 5.5 Gy ((60)Co gamma-ray) on day 0 followed by allogeneic hematopoietic stem cell transplantation (allo-HSCT). The allo-grafts consisted of 2 x 10(7) peripheral hematopoietic stem cells from mobilized male BALB/c (H-2(d)) donor mice with the granulocyte colony-stimulating factor (G-CSF). Day 2 after allo-HSCT, the recipient mice were given 200 mg/kg cyclophosphamide intraperitoneally. Afterwards these recipient mice were infused 2 x 10(6) sensitized or unsensitized-donor lymphocytes at the 28 days after transplantation. The results showed that the mice receiving sensitized-donor lymphocyte infusion did not suffer from GVHD and the phenotypic character of the recipient mice (black color) converted to that of the donor mice (white color), and to become full-donor chimerism. It was found that the ratio of CD4(+)/CD8(+) T lymphocytes of them decreased at the earlier period and increased after half month, but which were also lower than that of the normal value. While various grades of acute GVHD was observed in that of the control group and the mixed-chimeras were maintained, though it increased a little, and the ratio of CD4(+)/CD8(+) T lymphocytes increased at first, then decreased to the normal level half month later. It is concluded that sensitized DLI converted mixed to complete donor chimerism without GVHD, and the rate of CD4(+)/CD8(+) has close relation to the incidence of GVHD.