Transplantation of CD34 human cells into mice with severe combined immunodeficiency results in functional T cells 4 weeks after transplantation

OBJECTIVE: Our purpose was to determine whether transplantation of fetal hu man CD34(+) cells into mice with severe combined immunodeficiency results i n functional T cells. STUDY DESIGN: The cells used in this study were isolated from fetal human l iver tissue obtained after elective termination of normal 18- to 24-week pr egnancies. Women with medical conditions that could confound the outcome we re excluded. Cells were labeled with fluorochrome-conjugated antibodies tha t recognized CD34 or other cell surface antigens. The cells were then sorte d with the use of a fluorescein-activated cell sorter. The human sorted cel ls were injected intraperitoneally in mice with severe combined immunodefic iency. Four groups of mice were studied: group 1, injected with 10(5) CD34( +) cells (n = 17); group 2, injected with 10(5) CD34(-) cells (n = 14); gro up 3, injected with 10(6) unsorted cells (n = 19); and group 4, sham-inject ed with phosphate-buffered saline solution as controls (n = 14). At 1, 2, a nd 4 weeks after transplantation, the peripheral blood monocytes of the stu dy mice were analyzed for functional T cells. Aliquots of cells (10(5)) wer e incubated for 48 hours with 0, 5, 10, and 20 mu g of phytohemagglutinin. Thereafter the cells were treated with 1 mu Ci of tritiated thymidine. Subs equently the incorporation of tritiated thymidine was determined by liquid scintillation counting. RESULTS: Cells from mice transplanted with either unsorted cells, sorted CD 34(+) cells, or CD34(-) cells showed a response to phytohemagglutinin that varied with time and with the mitogen concentration. Even though unsorted f etal human liver cells had a maximal response at 2 weeks, this posttranspla ntation response was not statistically significant. CD34(+) cell response t o phytohemagglutinin was significant at 4 weeks after transplantation. CD34 (-) cells also had a peripheral blood cell response at 4 weeks after transp lantation; however, this response was not statistically significant. In add ition, all mice transplanted with fetal human liver cells had some function al T cells at 4 weeks; however, this response was statistically significant only for CD34(+) cells. CONCLUSION: Transplantation of either sorted CD34 (positive or. negative) c ells or unsorted fetal human liver cell preparations into mice with severe combined immunodeficiency results in functional T cells. However, only the mice with transplanted CD34(+) cells demonstrated a statistically significa nt response.