Azathioprine lowers your body's immune system. The immune system helps your body
fight infections. The immune system can also fight or "reject" a transplanted organ such as a
liver or kidney. This is because the immune system treats the new organ as an invader.
Azathioprine is used to prevent your body from rejecting a transplanted kidney. It is also
used to treat symptoms of rheumatoid arthritis.
Azathioprine may also be used for other purposes not listed in this medication guide.