CEACAM8 (CD66b) is a cell surface glycoprotein expressed on neutrophils that mediates calcium-independent cell adhesion 1. It functions as a heterophilic adhesion molecule, primarily binding to CEACAM6 rather than exhibiting homophilic interactions 1. The N-domain is critical for these adhesive interactions 1. CEACAM8 is stored in neutrophil granules and can be upregulated from intracellular stores or released as a soluble form in response to stimuli 2. Soluble CEACAM8 interacts with CEACAM1 on airway epithelial cells, inhibiting TLR2-triggered inflammatory responses through ITIM-mediated signaling and SHP-1 recruitment 3. This represents a mechanism by which neutrophils dampen excessive inflammation during bacterial infections 3. CEACAM8 is released by granulocytes in response to bacterial DNA via TLR9-dependent pathways 3. Clinically, CEACAM8 emerges as a predictive biomarker for anti-TNF drug responsiveness in pediatric inflammatory bowel disease 4 and has been identified as a potential diagnostic marker in major depressive disorder 5. Beyond classical neutrophil functions, CEACAM8 participates in immune regulation and inflammatory resolution.