Effect of papain pretreatment on islet allograft survival Isolated BALB/c islets were pretreated with various papain concentrations (0, 0.1, 1, and 10 mg/mL) prior to islet transplantation. Two hundred islets were transplanted under the left KC. (A) Individual blood glucose readings for a cohort of papain-pretreated islet-transplanted C57BL/6J mice. As indicated by the arrow, nephrectomies were performed on recipient mice that survived up to 120 d after receiving an islet allograft. (B) Survival of islet allografts (BALB/c to C57BL/6J) in recipient mice. The MSTs were calculated and compared using the Kaplan-Meier method. (C) Histological analysis of the grafts of 0 and 1 mg/mL papain groups (upper panels: 0 mg/mL papain (day 14); middle: 1 mg/mL papain (day 14); lower: 1 mg/mL papain (day 120)). Islet grafts were harvested on days 14 or 120 after transplantation. Paraffin-embedded sections were stained with HE, and anti-insulin and -Foxp3 antibodies. Arrowheads indicate Foxp3-positive cells. (HE and insulin staining: original magnification, ×100; Foxp3 staining: left, ×200 and right, ×400).