Exosomes from cytokine-treated cells induce apoptosis of recipient naïve beta-cells. Exosomes were isolated from the media of MIN6B1 cells cultured for a total of 48 h and treated with a combination of pro-inflammatory cytokines (IFNγ, TNF-α and IL-1β) for 0 h (Exo-Ctl), 24 h (Exo-cyt 24 h) or 48 h (Exo-cyt 48 h). Recipient naïve MIN6B1 cells (A, C, D) or dispersed mouse islet cells (B) were incubated with the different exosome populations for 72 h and then functionally characterized. A, B) Cell death was assessed by scoring the cells displaying pycnotic nuclei upon Hoechst staining. C) Beta-cell proliferation was assessed by BrdU incorporation. D) Insulin secretion at 2 or 20 mM glucose was measured by ELISA and was expressed as percentage of insulin content (IC). The results are means ± SD of at least four independent experiments. *Significantly different from control condition (Exo-Ctl), p ≤ 0.05 by ANOVA analysis, Dunnett’s post-hoc test.