Making Eosinophils Through Subtle Shifts in Transcription Factor Expression

More than a century after eosinophil granulocytes were baptized by Paul Ehrlich their role in defense mechanisms against parasitic infections and in allergic reactions has been firmly established (1). In contrast to the wealth of functional knowledge about these cells, their developmental origin, relationship to other blood cell types, and the critical transcription factors that determine their fate have long been elusive. Work in the 1990's showed a key role of both GATA and C/EBP transcription factors through experiments in which their expression was enforced in transformed chicken and murine cell lines. In addition, eosinophil-specific promoters were found to be regulated by an interplay between these factors. In several new papers this concept has been confirmed and applied to the reprogramming of normal human and murine cells. In addition, two studies show that GATA-1–deficient mice lack eosinophils, nicely complementing earlier work that demonstrated...