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  3. For several years, scientists have been testing a substance called interferon, a potential wonder drug that is proving to be eff

For several years, scientists have been testing a substance called interferon, a potential wonder drug that is proving to be eff

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问题     For several years, scientists have been testing a substance called interferon, a potential wonder drug that is proving to be effective in treating a variety of ailments, including virus infections, bacteria infections, and tumors. To date, the new drug has provoked no negative reaction of sufficient significance to discourage its use. But in spite of its success, last year only one gram was produced in the entire world.
    The reason for the scarcity lies in the structure of interferon. A species specific protein, the interferon produced from one animal species cannot be used in treating another animal species. In other words, to treat human beings, only interferon produced by human beings may be used. The drug is produced by infecting white blood cells with a virus. Fortunately, it is so potent that the amount given each patient per injection is very small.
    Unlike antibiotics, interferon does not attack germs directly. Instead, it makes unaffected cells resistant to infection, and prevents the multiplication of viruses within cells.
    As you might conclude, one of the most dramatic uses of interferon has been in the treatment of cancer. Dr. Hans Strander, research physician at Sweden’s famous Karohnska Institute, has treated more than one hundred cancer patients with the new drug. Among a group of selected patients who had undergone surgical procedures for advanced cancer, half were given conventional treatments and the other half were given interferon. The survival rate over a three-year period was 70 percent among those who were treated with interferon as compared with only 10 to 30 percent among those who had received the conventional treatments.
    In the United States, a large-scale project supported by the American Cancer Society is now underway. If the experiment is successful, interferon could become one of the greatest medical discoveries of our time.
What effect does interferon have on infection?
选项 A、It provokes a negative reaction.
B、It keeps healthy cells from becoming infected.
C、It causes healthy cells to grow.
D、It attacks viruses.
答案B
解析 文中第三段第二句中说：“……它使未受感染的细胞对传染病有抵抗能力，防止病毒在细胞内繁殖。”由此我们可以得出，它的作用就是使健康细胞避免受感染。故选项B正确。
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