The concentrations per milliliter of short-term survival of donor leukocyte subpopulations (including CD4, CD8, CD15, and CD19) derived from QAS-PCR results for the six female tx recipients who had detectable male cells 3 to 4 days post-tx. The pre- and post-tx serial frozen whole-blood samples collected from six female recipients were subjected to enrichment of leukocyte subpopulations including CD4, CD8, CD15, and CD19 cells, followed by amplification and quantitation using Y-chromosome–specific primers. The y-axis represents the concentration of donor cells per milliliter of recipient’s blood.