Transcription factor Growth factor independence 1 (Gfi1) is required for 
multilineage blood cell development, from stem and progenitor cells to 
differentiated lymphoid and myeloid cells. Gfi1 expression is rapidly induced by 
cytokines that control both the adaptive and innate immune systems. Gfi1 itself 
represses the expression of genes implicated in cell survival, proliferation and 
differentiation. Changes in Gfi1 expression and function have not only been 
implicated in neutropenia, allergy, autoimmunity and hyperinflammatory 
responses, but also in lymphoma and more recently in the development of 
leukemia. In this study, we review how Gfi1 and its paralogue Gfi1b control the 
development of blood cells, discuss how changes in Gfi1 and Gfi1b function 
contribute to hematological disease and report on the molecular function of 
these proteins.