Streptococcus is a common bacterial infection that triggers a response from the immune system to fight the infection. Occasionally, people infected by
Streptococcus have jerky body movements, but
Streptococcus does not infect the brain or muscles, parts of the human body that control body movements. Christopher Pittenger and his team hypothesize that the jerky body movements are the result of the immune system mistakenly targeting brain tissue instead of the
Streptococcus infection. To test their hypothesis, the researchers extracted antibodies from human patients with jerky body movements and injected those antibodies into mice.
Which finding from Pittenger's and his team's research, if true, would most directly support their claim?
Correct
Incorrect
The question asks you to support Pittenger's claim, so skim the text to identify it. Pittenger's name and the keyword "hypothesize" in the third sentence marks the claim: "jerky body movements" are caused by the immune system attacking the brain instead of a Streptococcus infection. A quick glance at the choices indicates they all refer to "antibodies," so read the text from the beginning looking for connections to the claim.
The first sentence defines Streptococcus as a common infection targeted by the immune system. The second sentence describes a paradox: sometimes "jerky body movements" result from these infections, but Streptococcus does not attack the body systems responsible for these movements. Refresh your memory of the claim in the third sentence: Pettinger and his team believe these movements are caused by the immune system attacking the brain by mistake. The fourth sentence describes how they are going to test this hypothesis; they will extract antibodies from humans with jerky body movements and put the antibodies into mice. Predict that the correct answer will have something to do with these antibodies attacking the brain, which is the key concept of the claim.
Choice (A) matches the prediction and is correct. If you ignore the scientific language, then the choice reads "The antibodies attacked . . . an area of the brain known to be associated with movement disorders," which directly supports the claim. Choice (B) makes the claim less likely, because the antibodies affected the muscles, not the brains, of the mice. Choice (C) is irrelevant because the text does not discuss the effects of an impaired immune system on either humans or mice. Choice (D) is an irrelevant comparison because the structure of the antibodies is never mentioned in the text.
