This causes inflammation and stiffness as rogue immune cells eat away cartilage and eventually erode bone. The disease mostly strikes women, usually between ages 25 and 50. Within 10 years, about half are too disabled to work. The machine is a column filled with silica and ''protein A,'' a protein from the cell wall of a bacterium that clings to human antibodies. As plasma runs through the column, the ''protein A'' separates out a small amount of antibodies before the plasma is retransfused, Provost said.
Antibodies are immune cells that fight off infections in healthy people.
In rheumatoid arthritis, some antibodies are believed to go out of control. Just how Prosorba works is unclear, because scientists do not know exactly which antibodies it removes from blood. It doesn't remove enough to account for all of the effect, so the company is doing further research to understand how Prosorba helps, said Cypress chief executive Dr. Jay Kranzler. For Merrill Meyer of Tempe, Ariz., the improvement was dramatic. To be treated, rheumatoid patients would go to blood banks or other designated Prosorba centers with experience in blood-filtering techniques.