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