The CD170 antibody targets Siglec-5 (sialic acid-binding immunoglobulin-type lectin-5), a cell surface protein belonging to the Siglec family, which plays roles in immune modulation by recognizing sialylated glycans. Expressed primarily on myeloid cells, such as neutrophils and macrophages, Siglec-5 interacts with sialic acid-containing ligands to regulate immune responses, often dampening activation to maintain tolerance or prevent excessive inflammation. CD170/Siglec-5 is implicated in both physiological and pathological processes, including cancer immune evasion, as some tumors exploit its inhibitory signaling to suppress anti-tumor immunity. In research, CD170 antibodies are used as tools to study Siglec-5's function in diseases like leukemia, autoimmune disorders, and chronic inflammation. Monoclonal antibodies against CD170 enable detection of protein expression via flow cytometry or immunohistochemistry, while blocking antibodies help investigate its immunosuppressive role. Therapeutic potential is also explored, with antibody-based strategies aiming to either block inhibitory signals in cancer or modulate immune activity in autoimmunity. Challenges include understanding context-dependent roles, as Siglec-5 may exhibit dual functions in different microenvironments. Overall, CD170 antibodies serve as critical reagents in deciphering immune regulation mechanisms and developing targeted therapies.