After 1980, research in the interferon field progressed rapidly as recombinant DNA technology clarified the relationship between the many interferon species and allowed the production of pure interferon on the kilogram scale. Most importantly, the generation of interferons on an industrial scale led to legitimate clinical applications. In 1987, Hillel Panitch, MD, and colleagues conducted a clinical trial with interferon gamma in patients with relapsing-remitting multiple sclerosis (MS).7 At that time, many MS experts considered MS to be a viral, postviral, or paraviral disorder, which made interferon gamma a plausible intervention. Unexpectedly, a disproportionate number of patients displayed disease exacerbations, and bioassays detected an increase in circulating HLA-DR–positive monocytes in peripheral blood of recipients. These observations strongly suggested that MS disease exacerbations are immune mediated and not the consequence of viral illness.