#22- Multiple sclerosis is an autoimmune disease: white

[desmail]

Hi,

I can see why (A) is correct (because if gamma interferon stopped white blood cells from producing myelin-destroying compounds then the patients wouldn't have gotten worse), but I am confused as to why B and C are wrong.

For (B), it mentions those who do not have multiple sclerosis, when we are only talking about those patients who DO have it, so why isn't this the answer?

For (C), the stimulus says nothing about what happens before and after the attacks, so im thinking this could be the answer too.

Is this a Cannot be True question? If it is, then maybe anything that could be true (anything not mentioned in the stimulus) will not be the answer?

Thank you in advance!
Dana

[Jon Denning]

Hey Dana – thanks for the question. This is indeed a Cannot Be True question, so the correct answer choice will be the one that is disproven by the information in the stimulus. Answers B and C are both potentially compatible with the stimulus info: for B we can’t know what happens when gamme interferon is given to non-MS patients, and for C there’s no information about what happens to gamme interferon levels just before and during an MS attack. Since B and C are not ruled out by the stimulus, they are incorrect here.

For answer choice A, we know that white blood cells attacking nerves’ myelin sheaths is how MS works, and we know that gamma interferon makes it dramatically worse. So it is incompatible to think that gamma interferon STOPS white blood cells from attacking myelin. This is the opposite of what the information in the stimulus suggests, so A cannot be true.

I hope that helps!

[cboles]

With what is said above I don't understand why E would be incorrect then. Gamma was proven not to work in treating MS and, in fact, made it worse so wouldn't E work?

[Nikki Siclunov]

Hi cboles,

Thanks for your question. Indeed, gamma interferon made MS worse. So, it's not unreasonable to suspect that a drug used to treat MS actually inhibits the activity of gamma interferon (IFNg). While such an inhibitory property is by no means required for such a drug to work, it's possible that the activity of IFNg is indeed inhibited by the drug in question. Please elaborate on why you consider this fact to be incompatible with the information contained in the stimulus.

Thanks!

[avengingangel]

jon, you mention in your explanation "we know that gamma interferon makes it dramatically worse" — how do we know that ?? in the stimulus, the words "they began testing gamma interferon" was really confusing to me...what does that mean, "test" it ? ftom the explanations here, it seems like that means the scientists "gave more" of the GI to the patients??? i was also thinking it could mean they took it away, or disabled it somehow, and thus the patients got sicker (making GI a good thing to have..) just not sure how i would be able to figure this out on test day from this stimulus. i read over this numerous times and don't really find support or clarification within the stimulus. i only got the question right bc i went thru & tried to categorize which answer choices made GI seems GOOD or BAD & figured that A was the outlier (the other ones made it seem bad/neutral), so i went with that one ! ha!

thanks.

[Eric Ockert]

Notice that the scientists began "testing" gamma interferon because they believed multiple sclerosis was triggered by chronic viral infections. As gamma interferon is one of the body's antiviral weapons, I think it is safe to assume here that the scientists are either providing this substance to the test subjects or at least increasing it if they already have it. Either way, it seems patients were getting MORE gamma interferon. Also, note that the results were "to their horror" which indicates a contrary result to what they expected.

There is enough here within the context of the stimulus to reinforce the assumption that scientists were adding gamma interferon during these tests. I think the LSAT would have to use much more specific language to leave open the possibility that scientists were withholding the substance or deactivating it.

Hope that helps!

[lsatnoobie]

Knowing now that this is a Cannot Be True question helps clarify everything so much, but prior to knowing this I could not justify anything. How can I correctly infer questions like these = cannot be true in the future?

[Adam Tyson]

It's a weird one, isn't it, noobie? Here's how to break it down:

The stem asks about LEAST (and they are kind enough to put that in all caps). That works the same as an EXCEPT question stem, in that the stem describes the four wrong answers. In this case, that means the four wrong answers ARE compatible with the stimulus. The correct, credited response will NOT be compatible (even though they said LEAST, the correct answer will almost certainly be incompatible, so that you do not have to make a subjective judgment - the LSAT tests logic, not judgment).

So what does "compatible" mean on the LSAT? Sort of like real life, it means they get along. More formally, it means that the two things are capable of coexisting without involving any paradox. It's possible that they are both simultaneously true. Incompatible, then (which is what your correct answer must be), means that the two things cannot logically coexist. One of them conflicts with the other. If one is true, the other cannot be.

And there we are - we've uncovered that this odd language is just another way of asking a Cannot Be True question! Four wrong answers are possible (because they are compatible with the claims in the stimulus), and one is impossible (because it is incompatible with the claims in the stimulus)! That was an ugly way to ask a simple question, wasn't it? That's why the authors of this test better hope we never run into them in a dark alley, amiright?