Granzyme B, a 32 kD serine protease also known as granzyme-2, serine protease B, CCP1, Asp-ase, and CTLA-1, is predominantly stored in the granules of cytotoxic T lymphocytes and NK cells. Low expression levels have been found in granulocytes, B cells, and activated dendritic cells. It plays a crucial role in rapid cell death and apoptosis by interacting with the mannose-6-phosphate receptor.