Importantly, our data suggests that during infection and inflammation, leukocytes may switch from a serglycin-dependent storage mode into a serglycin-independent mode of constitutive expression and secretion, as seen for cytotoxic T cells expressing granzyme B during virus infection [51], for MCs expressing the MC-specific proteases MCPT4, MCPT5, MCPT6 and CPA3 during infection with T. gondii [24], and for neutrophils expressing elastase (NE) during T. spiralis infection as shown in this study. Here, CPA3 is linked to viral infectious disease.