SH2D1B encodes EAT-2, a cytoplasmic adapter protein that regulates signaling through SLAM family receptors, particularly in natural killer (NK) cells. The protein plays a crucial role in NK cell-mediated cytotoxicity by controlling signal transduction through CD244/2B4 and SLAMF7 receptors, affecting downstream signaling pathways including PLCG1 and ERK activation 12. SH2D1B expression is critical for maintaining NK cell function, as transcriptional suppression by ZNF683 leads to NK cell exhaustion and impaired cytotoxic activity in multiple myeloma 1. In type 1 diabetes, SH2D1B-high NK cells activate the IFNγ/JAK1/STAT/CD38 pathway, potentially producing adenosine to limit autoimmunity 3. The gene shows clinical significance across multiple diseases: high SLAMF7/SH2D1B co-expression correlates with better survival in neuroblastoma patients 4, while altered methylation patterns affect autoimmune thyroiditis development 5. SH2D1B also serves as a biomarker for various conditions including colorectal cancer screening 6, Vogt-Koyanagi-Harada disease 7, and birdshot chorioretinopathy, where CD8bright CD244bright NK cells expressing SH2D1B rapidly decline upon clinical remission 2.