TCF3 (Transcription Factor 3), also known as E2A, is a helix-loop-helix (HLH) transcription factor encoded by the TCF3 gene. It plays critical roles in regulating gene expression during cellular differentiation, particularly in early B-cell and T-cell development. TCF3 binds to E-box DNA motifs (CANNTG) to activate or repress target genes, often partnering with tissue-specific regulators like EBF1 or ID proteins to modulate lymphoid lineage commitment. Its function is essential for V(D)J recombination, a process that generates diverse antibody repertoires in adaptive immunity. Dysregulation of TCF3 is linked to hematological malignancies, including pre-B-cell acute lymphoblastic leukemia (ALL), where chromosomal translocations (e.g., TCF3-PBX1) result in oncogenic fusion proteins. TCF3 antibodies are widely used in research to study its expression, localization, and interactions via techniques like Western blotting, immunoprecipitation, chromatin immunoprecipitation (ChIP), and immunofluorescence. These antibodies help elucidate TCF3's role in normal immune cell maturation, its crosstalk with signaling pathways (e.g., Wnt/β-catenin), and its involvement in diseases. Additionally, TCF3 is implicated in maintaining pluripotency in embryonic stem cells, expanding its relevance to regenerative medicine and cancer biology studies.