GZMB also known as granzyme B is crucial for the rapid induction of target cell apoptosis by CTL in cell-mediated immune response. Cytolytic T lymphocytes (CTL) and natural killer (NK) cells share the remarkable ability to recognize, bind, and lyse specific target cells. They are thought to protect their host by lysing cells bearing on their surface nonself antigens, usually peptides or proteins resulting from infection by intracellular pathogens. Recombinant human GZMB, fused to His-tag at N-terminus, was expressed in E.coli.