GZMB (Granzyme B): GZMB is a serine protease produced by cytotoxic T lymphocytes and natural killer (NK) cells. It plays a key role in the immune response by inducing apoptosis in virally infected or tumor cells through cleavage of specific intracellular substrates. Proper function of GZMB is essential for effective immune surveillance, and its dysregulation can lead to weakened defense against infections and cancer, highlighting its importance in immune protection and cellular balance.