Researchers at Stanford found that in people with relapsing-remitting multiple sclerosis (RRMS), there seem to be 2 types: one type characterized by high levels of an immune cell called interleukin-17 (IL-17) in the blood and the other type with a low level of IL-17 in the blood. Turns out that the interferon-based disease modifying drugs (Avonex, Betaseron, Rebif) have different effects on people, depending on their level of circulating IL-17:

Interferons are NOT great for people with higher IL-17: In this study, people who did NOT respond to interferon-beta had higher levels of IL-17 (actually, a specific variety of IL-17, called IL-17F), compared to people who did well on the interferons. The people with the higher levels of IL-17 had more relapses.

In fact, the study showed that in the people with higher IL-17, the interferons were proinflammatory, meaning that they may have actually made the disease worse.

Interferons are effective in people with low IL-17: However, the interferon drugs were effective in those people who had very low levels of IL-17F in their blood. These people experienced no relapses while on the drugs.

It appears that about one-third of people with RRMS have high levels of IL-17.

Of course, upon hearing of this information, people with MS (especially those currently using interferon-based drugs or considering using them) will want to get tested to see whether they are in the "high IL-17" or "low IL-17" category. I could not find out whether or not the blood test to measure IL-17 levels is widely available at this point - I suspect it is not, but that it will be (or could be) soon.

However, I am not sure what docs will do with this information at this point. Assuming that there was a way to test people, this is still a pretty small study (only 26 people participated), so I don't know if docs will want to switch people off of interferons if they seem to be doing well so far, regardless of what this data shows. My guess is that if the patient tested high for IL-17 and had not yet tried Copaxone (which is NOT an interferon-based drug), that might be a logical move. If Copaxone hadn't worked in the past, and there were high levels of IL-17, I don't know what the next move would be, especially if the patient was doing fine on the drug. I can't be sure that many docs would be ready to go for Tysabri (or take the patient off of all treatment), based on this limited data.

The other side of the story is that the researchers think that this might be hugely good news for people with low IL-17 levels, as it looks like the interferons work exceptionally well in these people. Would the low IL-17 people that may have had a relapse or two on Copaxone be switched to an interferon?

I guess we will need to wait and see, but this seems like the kind of fairly inexpensive, easy to replicate study that should be given priority, as there are thousands of people on these drugs. Of course, billions of dollars are at stake (many of the articles about this study were in the business sections). However, more importantly, people could be wasting time or even doing themselves harm on these drugs. A larger study could answer a lot of questions.

http://ms.about.com/b/2010/03/30/interferons-not-good-for-some-people-with-ms.htm