Variables to predict engraftment of umbilical cord blood into immunodeficient mice: usefulness of the non-obese diabetic-severe combined immunodeficient assay

Umbilical cord blood is an alternative stem cell source for patients withou t matched family donors. In this study, we examined several parameters that have not been studied in detail - radiation dose, cell dose, age of mice, and maternal and neonatal characteristics of the cord blood donor - that af fect engraftment of cord blood in non-obese diabetic-severe combined immuno deficient (NOD-scid) mice. Engraftment, measured using flow cytometry analy ses of human CD45(+) cells, was highest in 400 cGy-treated mice. Successful engraftment was demonstrated up to 6 months, with a mean engraftment of 31 % (range 0-67%) of human cells in recipient bone marrow. Engraftment was sk ewed to B lymphocytes. The radiation dose of 350 cGy resulted in superior s urvival of the murine recipients compared with 400 cGy (P = 0.03). The sex of the NOD-scid recipients had a significant effect on survival (female sup erior to male, P = 0.01), but not on engraftment. There were high levels of variability among different cord units and among animals injected with the same cord unit. This variability may limit the clinical usefulness of the NOD-scid mice as hosts for the quantification of human stem cells.