The Ausimmune Study, conducted between 2003 and 2007, was a significant multi-centre case-control study in Australia that focused on understanding how environmental factors influence immune diseases, particularly multiple sclerosis (MS). The study found that the risk of a first demyelinating event (FDE), which could lead to MS, varied by latitude, with higher risks in regions with less sun exposure. It also highlighted the protective effects of higher vitamin D levels, a healthy diet, and certain lifestyle choices, like avoiding smoking, in reducing the risk of MS. These findings have informed ongoing research and clinical trials aimed at preventing and managing MS.