(A) Representative sections of FOXP3-stained GFP– or human A20–transduced islet allografts at postoperative day (POD) 10 (n = 4 GFP and 4 A20), (B) POD 15–25 (GFP grafts taken before rejection; n = 6 GFP and 7 A20), and (C) POD > 100 (n = 6). Scale bar: 100 μm. (D) Quantification of FOXP3+ T cells. (E) GFP- or A20-expressing grafts harvested at POD 10, as well as A20-expressing long-term–surviving grafts harvested at > POD 100 and subjected to reverse transcription PCR (RT-PCR) for known immune regulatory factors. Nontransplanted overnight-cultured isolated islets were used as baseline. Each point represents an individual islet graft. (F) Flow cytometric analysis of CD4+CD25+Foxp3+ T cells from the spleen (SPLN), renal lymph node (RLN), and blood (BLD) from C57BL/6 mice (WT; n = 5) and C57BL/6 recipients harboring long-term–surviving A20 transduced grafts (A20; n = 5). Error bars ± SEM and statistical significance determined by 1-way ANOVA with Tukey’s multiple comparisons post hoc test; *P < 0.05.