CD34⁺CD38⁻ cord blood cells are immunophenotypically uncommitted to lymphoid or myeloid lineages. Three-color analysis of CD34⁺ enriched cord blood cells from region R1 (based on forward and side scatter (not shown9). (B) Region R2 defining CD34⁺CD38⁻ cells (ie, high CD34 expression with CD38 expression less than half the maximal fluorescence of the isotype control). R2 comprises 3.53% ± 0.68% (mean ± SEM) of all CD34⁺ cells (defined by upper and lower right quadrants). (C, D, and E) The lack of expression of lineage-specific antigens on cells from R2. (A and F) Respective isotype controls.