Ikaros, also known as IKZF1 (Ikaros family zinc finger protein 1) is a hematopoietic-specific transcription factor involved in the regulation of lymphocyte development, together with other members of this family, such as Aiolos and Helios. Ikaros forms homo- and heterodimers with these proteins and functions predominantly in early hematopoietic development. Expression of Ikaros, Aiolos and Helios is restricted to cells of the hematopoietic system, whereas other family members, Eos and Pegassus, are more widely expressed. Disruption of Ikaros leads to T and B cell leukemias.