Schematic representation of triple HLA-mismatched SCID-hu bone model.

In the SCID-hu bone assay, a candidate stem cell population is microinjected into an HLA-mismatched fetal bone fragment implanted in an immunodeficient mouse. The bone fragment is retrieved and flow cytometrically analyzed 8 to 10 weeks later for the presence of donor-derived multilineage hematopoiesis. In the triple HLA-mismatched SCID-hu bone model, 2 different donors bearing distinct HLA alleles are injected into the same fetal bone graft with a third distinct HLA type. At the termination of the assay, the multilineage hematopoietic contribution of each of the 2 donors as well as the contribution of the recipient is determined in a 5-color flow-cytometric assay using monoclonal antibodies specific for human HLA allotypes and for various hematopoietic markers.