FIGURE 4.

CatH has proGrB convertase activity in vivo. ProGrB (20 pmol) was incubated overnight at pH 5.5 with lysates from 1 × 10⁶ unstimulated splenocytes (A and B) or from 4 × 10⁵ allogeneic CTL (C) derived from wild-type BL/6 (WT), CatH^−/−, CatC^−/−, or CatCH^−/− mice. The resultant GrB activity was assessed using the quenched fluorescence substrate. Each assay was performed using lysates from three mice of each strain (with the exception of the CTL, where one wild-type BL/6 and two CatH^−/− lysates were used), and the mean ± S.E. was calculated. Student's t tests were performed, and p values indicate significant differences in activity generated by the CatC^−/− and CatCH^−/− lysates.