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

Abstract

Our purpose was to determine whether transplantation of fetal human CD34(+) cells into mice with severe combined immunodeficiency results in functional T cells. The cells used in this study were isolated from fetal human liver tissue obtained after elective termination of normal 18- to 24-week pregnancies. Women with medical conditions that could confound the outcome were excluded. Cells were labeled with fluorochrome-conjugated antibodies that recognized CD34 or other cell surface antigens. The cells were then sorted with the use of a fluorescein-activated cell sorter. The human sorted cells were injected intraperitoneally in mice with severe combined immunodeficiency. 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); group 3, injected with 10(6) unsorted cells (n = 19); and group 4, sham-injected with phosphate-buffered saline solution as controls (n = 14). At 1, 2, and 4 weeks after transplantation, the peripheral blood monocytes of the study mice were analyzed for functional T cells. Aliquots of cells (10(5)) were incubated for 48 hours with 0, 5, 10, and 20 micrograms of phytohemagglutinin. Thereafter the cells were treated with 1 microCi of tritiated thymidine. Subsequently the incorporation of tritiated thymidine was determined by liquid scintillation counting. Cells from mice transplanted with either unsorted cells, sorted CD34(+) cells, or CD34(-) cells showed a response to phytohemagglutinin that varied with time and with the mitogen concentration. Even though unsorted fetal human liver cells had a maximal response at 2 weeks, this posttransplantation response was not statistically significant. CD34(+) cell response to phytohemagglutinin was significant at 4 weeks after transplantation. CD34(-) cells also had a peripheral blood cell response at 4 weeks after transplantation; however, this response was not statistically significant. In addition, all mice transplanted with fetal human liver cells had some functional T cells at 4 weeks; however, this response was statistically significant only for CD34(+) cells. Transplantation of either sorted CD34 (positive or negative) cells 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 significant response.