It has been reported that in mature human cell lines, AK2 mediates mitochondrial apoptosis by binding to Fas-associated with death domain protein (FADD) and caspase-10.11, 12 The latter observation does not fit with our present data and the phenotype of RD.4, 5 Moreover, we found that AK2 knockdown in murine hematopoietic progenitors also impairs T-cell and neutrophil differentiation (data not shown). Here, AK2 is linked to reticular dysgenesis.