The Natural Killer Cell Antibody (H25) is a type of mouse monoclonal antibody that detects the Natural Killer Cell protein in humans. It is available in different forms, including non-conjugated and conjugated forms with various labels like agarose, HRP, PE, FITC, and Alexa Fluor®. Natural killer cells are a type of large, granular lymphocytes derived from the bone marrow and play a role in the innate immune defence. They are activated by interferons or cytokines released by macrophages. Instead of directly destroying microorganisms, NK cells target and attack infected cells. They have proteins like granzymes and perforin, which create pores in the target cell membrane, leading to its lysis. Individuals without NK cells are highly vulnerable to early stages of herpes virus infection.