Pancreatic islet production of murine interleukin-10 does not inhibit immune-mediated tissue destruction

IL-10 inhibits macrophage-dependent antigen presentation, cytokine production, and generation of allospecific cells in vitro. These findings have lead to the widespread expectation that IL-10 may be a useful immunosuppressive agent to inhibit allograft rejection or autoimmunity in vivo. We used two experimental paradigms to study effects of murine IL-10 on in vivo immune responses. First, fetal pancreata or adult pancreatic islets from transgenic mice expressing IL-10 in pancreatic β cells (Ins-IL-10 mice) were grafted across the MHC barrier to examine if IL-10 could inhibit allograft rejection. Second, Ins-IL-10 mice were crossed with transgenic mice expressing lymphocytic choriomeningitis virus (LCMV) antigens in pancreatic β cells. These mice were infected with LCMV to elicit autoimmune diabetes, allowing us to ask if IL-10 protects islets from autoimmune destruction. We observed that allografts from IL-10-transgenic donors were rejected with comparable kinetics to the rejection of control nontransgenic allografts, indicating that IL-10 does not inhibit allograft rejection. After LCMV infection, IL-10 and LCMV antigen double transgenic mice developed diabetes earlier than LCMV antigen single transgenic littermates, suggesting that IL- 10 does not inhibit islet antigen presentation or recognition. Our results contrast to in vitro observations and suggest that IL-10 cannot overcome immune-mediated tissue destruction within the pancreas.