Humira and Enbrel suppress the immune system. The printed documents that come with each will tell you that it does, and will tell you to stop taking it if you get sick so that your immune systems can better work against the sickness. Each also has warnings about other problems that can be caused by its immunosuppression, such as fungal infections and neurological disorders. I learned this the hard way, in that I got MS from taking Enbrel for four years.
I've since learned that I could control most of my pain through the low-starch diet and supplements. If I had known about that earlier, I would never have started Enbrel. But that's the kind of info the big pharmas want to suppress. Enbrel worked great for a while, but now I'm back to full-blown AS with severe MS symptoms.
--Greg