B-cells were purified from pooled LN (cervical, axillary, mesenteric and inguinal) of three 6-8 week old NOD (black bars), NOD.Idd5B10 (white bars), NOD.Idd9/11NOR (grey bars) and C57BL/10 female mice (striped bars) in experiment (A) or four 6-8 week old female NOD (black bars), NOD.Idd9/11NOR (grey bars) and NOR (dotted bars) mice in a separate Experiment (B). Triplicate aliquots of 1×105 B-cells were stimulated with 1 μg/ml goat anti-mouse IgM F(ab’)2 fragments with or without 5μg/ml CD40 specific mAb. Proliferation over the final 24 hours of a 72 hour incubation period was measured by [3H] thymidine incorporation and is shown as mean Δ cpm (stimulated – non-stimulated) ± SEM for triplicate wells of each strain.