Correction of anemia and dyserythropoiesis depends on the level of modified RBC, independently of the presence of tEpoR in the vectors. (□) Mice transplanted with LG/HA-Y1 transduced marrow cells. (■) Mice transplanted with LG-transduced marrow cells. (A) Correlation of total and human hemoglobin concentrations (Hb), erythrocyte counts (RBC), reticulocyte percentages (Retic), and spleen weight with modified RBC of transplanted β-thalassemic mice. Regression lines and 95% confidence intervals (dashed lines) were obtained from LG mice having a proportion of RBC⁺ greater than 40%. The bottom and top boundaries of the horizontally and vertically hatched boxes indicate mean ± SD of values from β-thalassemic and normal C57BL/6J mice. For hemoglobin, the bottom and top regression lines corresponds to therapeutic (human) and total hemoglobin, respectively. (B) Correlation of spleen weight with percentage of erythroid cells in the spleen. The regression line and 95% confidence interval were plotted with data from all mice. Three mice receiving mock-transduced cells were included (●).