Scientists have invented a novel way to halt and even reverse rheumatoid arthritis. They have developed an imitation of a suicide molecule that floats undetected into overactive immune cells responsible for the disease. Referred to as Casper the Ghost, the stealthy molecule causes the immune cells to self-destruct. The approach doesn’t carry the health risks of current treatments. The new therapy, tested on mice, stopped the disease cold in 75 percent of the animals.