Figure 4. Diabetes is unchanged in granzyme B-deficient NOD mice but is delayed in granzyme B-deficient NOD8.3 mice.

(A) The proportion of CD8⁺IGRP-tetramer⁺ T cells in freshly isolated islets from 100 day old female NOD or granzyme B^−/− mice was determined by flow cytometry (n = 3). No significant difference was observed. (B) Activated NOD8.3 or GrzB^−/−NOD8.3 CD8⁺ T cells were cultured for 16 hours with IGRP pulsed and ⁵¹Cr labeled NOD islets at an effector to target ratio of 20∶1. Data are mean±SEM of three independent experiments. No significant difference was observed. (C) A cohort of female NOD (n = 35) and granzyme B^−/− mice (n = 19) mice were observed for 300 days for the incidence of spontaneous diabetes. No difference was observed between the groups. Data analyzed by Log-rank (Mantel-Cox) Test. (D) Pancreata from NOD8.3 or GrzB^−/−NOD8.3 mice were harvested at 50 days of age for insulitis scoring on insulin antibody-stained frozen sections. Total islets scored: NOD8.3 = 596 islets, GrzB^−/− NOD8.3 = 508 islets. (E) For each mouse the insulitis score was calculated using the method as described in material and methods, and data are the mean±SEM insulitis score. Data analyzed by unpaired Student’s t test. ns = not significant. (F) Incidence of diabetes was studied in cohorts of NOD8.3 (n = 12) and GrzB^−/−NOD8.3 (n = 12) mice. The development of diabetes in GrzB^−/−NOD8.3 mice was significantly delayed compared to NOD8.3 (*p = 0.0399). Data analyzed by Log-rank (Mantel-Cox) test.