Investigation of donor lymphocytes infusion in mixed hematopoietic murine chimeras after nonmyeloablative peripheral blood stem cell transplantation

To study the recipient chimerism, the immune state and the dependability between them after infusion of donor lymphocytes(DLI) which were sensitized by the skin of recipient. Female C57BL/6 mice(H-2~(b)) as recipients received total body irradiation(TBI) of 5.5 Gy(~(60)Co X-ray) on day 0 followed by allogeneic peripheral blood stem cell transplantation. The allo-grafts consisted of 2×10~(7) peripheral hematopoietic stem cells from male BALB/c(H-2~(d)) donor mice mobilized by granulocyte colony-stimulating factor (G-CSF). Two days after allo-HSCT, the recipient mice were given 200 mg/kg cyclophosphamide intraperitoneally. Afterwards these recipient mice were infused with 2×10~(6) sensitized or unsensitized-donor lymphocytes at the day of 28 after transplantation. The results showed that the mice which received sensitized-DLI became full-donor chimerism at the 60 th day after transplantation. The ratio of CD4~(+)/CD8~(+) T lymphocytes of them decreased during the earlier period after DLI and increased half month later, but was still lower than the normal value. Recipients showed the specific hyporesponsiveness to donor mice through MLR assay. In unsensitized group, 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. The result of MLR also showed hyporesponsiveness, but it exceeded that of the sensitized DLI recipients. Mixed-chimerism could be achieved by using a nonmyeloablative TBI and CTX-based conditioning regimen combination with infusion of peripheral blood stem cells mobilized by rhG-CSF in fully H-2-mismatched recipient mice. Sensitized DLI converted mixed to complete donor chimerism. The rate of CD4~(+)/CD8~(+) and the reactiveness of MLR showed super dependability with the chimerism.