Transcription factor that plays an important role in the regulation of lymphocyte differentiation. Plays an essential role in regulation of B-cell differentiation, proliferation and maturation to an effector state. Involved in regulating BCL2 expression and controlling apoptosis in T-cells in an IL2-dependent manner. Homodimer. Heterodimer with other IKAROS family members. Interacts with IKZF4 AND IKZF5. Interacts with IKZF1. Interacts with HRAS. Interacts with FOXP3; this interaction may be required for silencing target genes and regulating the suppressive activity of FOXP3-positive regulatory T-cells (Treg). Interacts with BCL21L isoform Bcl-X(L); this interaction blocks the anti-apoptotic role of BCL21L. Associates with histone deacetylase complexes containing HDAC1, MTA2 and SIN3A. Expressed most strongly in peripheral blood leukocytes, the spleen, and the thymus. Up-regulated by TGFB1 and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in activated AHR T-cells. C2H2-type 5 and C2H2-type 6 mediate homodimerization and heterodimerization. Phosphorylation on tyrosine residues induced by IL2 is required for dissociation from HRAS and nuclear translocation of IKZF3 in T-cells. Phosphorylation on tyrosine residues induced by IL4 is required for dissociation from Bcl-X(L) in T-cells. The disease is caused by variants affecting the gene represented in this entry. Belongs to the Ikaros C2H2-type zinc-finger protein family.