DEAR DOCTOR K: I have rheumatoid arthritis and take anti-TNF drugs. I'd like to understand how they work.
DEAR READER: Rheumatoid arthritis (RA) is a chronic autoimmune disease in which the body's immune system mistakenly attacks healthy tissue in the joints. Our immune systems are not supposed to attack our own tissues; they're supposed to attack foreign things that enter our body, particularly germs. In autoimmune diseases, however, something goes haywire.