side effects of this drug and what is it used for ## Actimmune contains a bioengineered formation of interferon gamma. It's a protein that acts as a biological response modifier, it's used to stimulate your immune system. Side effects may include: headache, fever, diarrhea and vomiting. You can learn more about it here: Is there anything else I can help with? ## All of my joints ache and my back never stops hurting is this just part of the side effects or should i be concerned?