Multiple sclerosis is an autoimmune disease: white blood cells attack the myelin sheath that protects nerve fibers in the spinal cord and brain. Medical science now has a drug that can be used to successfully treat multiple sclerosis, but the path that led medical researchers to this drug was hardly straightforward. Initially, some scientists believed attacks characteristic of multiple sclerosis might be triggered by chronic viral infections. So in 1984 they began testing gamma interferon, one of the body' s own antiviral weapons. To their horror, all the multiple sclerosis patients tested became dramatically worse. The false step proved to be instructive however. Which one of the following is LEAST compatible with the results of the gamma interferon experiment? ['Gamma interferon stops white blood cells from producing myelin-destroying compounds.', 'Administering gamma interferon to those without multiple sclerosis causes an increase in the number of white blood cells.', 'The drug now used to treat multiple sclerosis is known to inhibit the activity of gamma interferon.', 'Medical researchers have discovered that the gamma interferon level in the cerebrospinal fluid skyrockets just before and during multiple sclerosis attacks.']