Granzymes are important factors secreted by cytotoxic T lymphocytes (CTLs) and natural killer (NK) cells. The family of human granzymes consists of five members, namely granzyme A, granzyme B (GZMB), granzyme H, granzyme K and granzyme M. As GZMB exerts a robust killing effect on tumours, it has garnered considerable attention. Currently, other cells in addition to CTLs and NK cells are known to produce GZMB in the presence of inducing factors or in specific environments, including TIM-3 + regulatory T cells (Tregs), 1 B lymphocytes, 2-4 plasma cells, 5 myeloid-derived suppressor cells, 6 macrophages, 7 mast cells, 8-10 basophils, 11 chondrocytes, 12 polymorphonuclear neutrophils, 13 CD4 + helper T cells, 14 neutrophils, 15 monocytes, 16 retinal pigment epithelial cells, 10 keratinocytes 17 and mesenchymal-like androgen-repressed human prostate cancer cells. 18 The diversity of GZMB-secreting cells may contribute to the complexity of GZMB functions; therefore, a comprehensive understanding of GZMB is extremely important for conducting extensive research on the innovative application of GZMB. | RELATIONSHIP AMONG PERFORIN (PRF1), GRANULYSIN (GNLY) AND GZMBPRF1, GNLY and GZMB are important molecules secreted by CTLs and NK cells that function synergistically to exert a killing effect. Studies conducted by Dotiwala et al have revealed that PRF1, GNLY and GZMB gain entry into cells