ID3 is a transcriptional regulator lacking a DNA-binding domain that functions primarily as a negative regulator of basic helix-loop-helix (bHLH) transcription factors through heterodimer formation. In myogenesis, ID3 inhibits muscle differentiation while promoting precursor cell proliferation 1. ID3 regulates immune responses by controlling macrophage activation; specifically, it shifts the macrophage inhibitory/activating receptor balance to promote anti-tumor activity by buffering transcription factor binding at the SIRPA locus 2. In T cell biology, ID3 identifies stem-like T cells and is essential for maintaining CD8 T cell responses during chr1 infection or cancer, enabling precursor exhausted T (Tpex) cell generation 3. As a p53 target gene, ID3 acts as a tumor suppressor in lung cancer by regulating E-cadherin expression and suppressing metastatic potential 4. In Burkitt lymphoma, ID3 mutations occur in approximately 70% of sporadic cases, fostering dependency on TCF3 signaling 5. Therapeutically, ID3 downmodulation enhances CAR T cell efficacy in solid tumors; ID3/SOX4 double-knockout CAR T cells demonstrate prolonged anti-tumor activity in pancreatic cancer 67. These findings establish ID3 as a multifunctional regulator with significant implications for cancer immunotherapy and lymphoma pathogenesis.