Recent studies have focused on the utility of soluble GrB in the blood as a biomarker of immune activation in humans with a variety of disorders, including autoimmune disease, graft rejection, and viral infection (Spaeny-Dekking et al., 1998; Tak et al., 1999; Goldbach-Mansky et al., 2005; Buzza and Bird, 2006; Altimari et al., 2008; Bem et al., 2008; Truong et al., 2008; Boivin et al., 2009). This evidence concerns the gene GZMB and viral infectious disease.