In response to viral infection, the immune systems of mice t

This topic has expert replies
Moderator
Posts: 426
Joined: Tue Aug 22, 2017 8:48 pm
Followed by:1 members
In response to viral infection, the immune systems of mice typically produce antibodies that destroy the virus by binding to proteins on its surface. Mice infected with a herpesvirus generally develop keratitis, a degenerative disease affecting part of the eye. Since proteins on the surface of cells in this part of the eye closely resemble those on the herpesvirus surface, scientists hypothesize that these cases of keratitis are caused by antibodies to herpesvirus.

Which of the following, if true, gives the greatest additional support to the scientists' hypothesis?

A. Other types of virus have surface proteins that closely resemble proteins found in various organs of mice.
B. There are mice that are unable to form antibodies in response to herpes infections, and these mice contract herpes at roughly the same rate as other mice.
C. Mice that are infected with a herpesvirus but do not develop keratitis produce as many antibodies as infected mice that do develop keratitis.
D. There are mice that are unable to form antibodies in response to herpes infections, and these mice survive these infections without ever developing keratitis.
E. Mice that have never been infected with a herpes virus can sometimes develop keratitis.

What's the best approach to determine the answer? Can any experts help?

User avatar
GMAT Instructor
Posts: 555
Joined: Wed Oct 04, 2017 4:18 pm
Thanked: 180 times
Followed by:12 members

by EconomistGMATTutor » Thu Nov 16, 2017 6:52 am
The conclusion: Keratitis in mice infected with a herpesvirus is caused by antibodies to herpesvirus.
The evidence: The immune systems of mice typically produce antibodies that destroy the virus by binding to proteins on its surface. Proteins on the surface of cells in the eye closely resemble those on the herpesvirus surface. Mice infected with a herpesvirus generally develop keratitis, an eye disease.

You are asked to support the conclusion/hypothesis. We are told that mice that produce the herpes antibodies get keratitis, the eye disease. Choice D, the correct choice, states that mice that DO NOT produce antibodies in response to herpes DO NOT get keratitis. This strongly supports the claim that the antibodies cause the keratitis.

Choice A is an "other" choice. We are not concerned with other types of viruses.
Choice B refers tells us that mice that cannot form antibodies to herpes get herpes at about the same rate as those mice that can form the antibodies. This is not a relevant comparison. What about the keratitis?
Choice C actually weakens the conclusion. If some mice don't get keratitis even though they produce antibodies, then it seems that the antibodies are not causing keratitis.
Choice E also weakens the conclusion. If a mouse does not get herpes, then it won't get the herpes antibodies. This choice says that these mice, without herpes, still can get keratitis. Therefore, the antibodies didn't cause the keratitis.

I'm available if you'd like a follow-up.
GMAT Prep From The Economist
We offer 70+ point score improvement money back guarantee.
Our average student improves 98 points.

Image