Antiapoptotic effect of KL with and without Dex in HPC erythroid cultures. Numbers of apoptotic cells/10⁶ erythroblasts evaluated during erythroid differentiation of normal, β-TI, and β-TM HPCs grown in the absence (C) or presence of KL (100 ng/mL), alone or in combination with Dex (10⁻⁸ M). At different days erythroid cells were harvested and processed for the evaluation of apoptotic cells using the annexin V binding assay. Mean (± SEM) values from 8 separate experiments carried out on 8 different donors are shown. The differences between the normal and β-TI or β-TM control growth curves are highly significant by analysis of variance (P < .001).