GZMB (Granzyme B): GZMB is a serine protease produced by cytotoxic T lymphocytes and natural killer (NK) cells. It plays a critical role in the immune response by triggering apoptosis in virus-infected or tumor cells through the cleavage of specific intracellular substrates. Proper function of GZMB is crucial for effective immune surveillance, and its dysregulation can result in decreased defense against infections and cancer, underscoring its importance in immune protection and cellular homeostasis.