Aims/hypothesis: T-cell activation by specific antigen has been found to increase macrophage migration inhibitory factor (MIF) expression, indicating its role as an important feature of T-cell activation in vitro and in vivo. To date, the potential role of MIF in the development of autoimmune-mediated diabetes mellitus has not been studied.
Methods: MIF-mRNA expression in splenic lymphocytes of spontaneously diabetic non-obese diabetic (NOD) mice (n=6), cyclophosphamide-treated NOD mice (n=6), 14-day-old non-diabetic NOD mice (n=7) and C57/Bl6 control mice (n=6) was monitored using an internally standardised competitive reverse transcription-polymerase chain reaction, and the MIF-protein levels were determined using Western blot analysis. In addition, the impact of intraperitoneally administered recombinant MIF-protein treatment on diabetes incidence in NOD mice was evaluated.
Results: MIF-mRNA expression was markedly increased in splenic lymphocytes of spontaneously diabetic NOD mice as well as in 8-week-old NOD mice treated with cyclophosphamide compared with 2-week-old non-diabetic NOD and healthy C57BL/6 control mice. Western blot analyses showed decreased lymphocytic MIF-protein content in diabetic as well as in cyclophosphamide-treated animals compared with 2-week-old non-diabetic NOD and healthy C57BL/6 mice, probably as a consequence of increased protein secretion. Furthermore, treatment of NOD mice with recombinant MIF-protein at 25 microg twice a week, from age 6 to 11 weeks, led to an increased diabetes incidence (86%; n=7) compared with untreated control groups (55%; n=20) at week 34.
Conclusions/interpretation: In this study, we report for the first time that MIF-mRNA expression in splenic lymphocytes is up-regulated during development of cell-mediated diabetes in non-NOD mice. The data of our preliminary study suggest a possible role of MIF in autoimmune-inflammatory events, such as type-1 diabetes and also that anti-MIF therapeutic strategy might serve to attenuate autoimmune processes.