As greater than 80% of skin aging is believed to be due to UV exposure (Gilchrest & Krutmann, 2006), and GzmB is expressed by many of the cells present or recruited after irradiation, we hypothesized that GzmB contributes to extracellular matrix degradation after UV irradiation through both direct cleavage of ECM proteins and indirectly through the induction of other proteinases, which leads to a phenotype of aged skin. This evidence concerns the gene GZMB and skin aging.