GNLY is synthesized as a 15-kDa molecule and then proteolytically cleaved at the amino and carboxyl termini to produce a 9-kDa form (Pena SV et al. 1997; Hanson DA et al. 1999). The 9 -kDa form of GNLY is confined to cytolytic granules that are directionally released by receptor-mediated granule exocytosis following target cell recognition (Hanson DA et al. 1999; Clayberger C et al 2012). In contrast, the 15-kDa form is constitutively secreted from distinct granules that lack perforin and granzyme (Clayberger C et al 2012). The 9-kDa GNLY exhibits cytolytic activity on the numerous microbes ranging from extracellular and intracellular bacteria to fungi and parasite (Stenger S et al. 1998; Ernst WA et al. 2000). GNLY kills Mycobacterium tuberculosis, the causative agent in tuberculosis and Plasmodium falciparum, a cause of malaria (Stenger S et al. 1998; Farouk SE et al. 2004). Alongside its ability to kill bacteria, fungi, and parasites, GNLY can block viral replication and trigger apoptosis in infected cells (Hata A et al. 2001).

Besides its direct antimicrobial activity, GNLY shows tumoricidal activity by inducing apoptosis in tumor cells. Both 9-kDA and 15-kDA forms of GNLY may also function as chemoattractants for T lymphocytes, monocytes and other inflammatory cells and activates the expression of a number of cytokines (Deng A et al. 2005; Castiello L et al. 2011).