2. 医学
  3. For several years, scientists have been testing a substance called interferon(干扰素), a potential wonder drug that is proving to b

For several years, scientists have been testing a substance called interferon(干扰素), a potential wonder drug that is proving to b

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问题     For several years, scientists have been testing a substance called interferon(干扰素), 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 of 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 powerful 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 Karolinska Institute, has treated more than one hundred cancer patients with the new drug. Among a group of selected patients who has undergone surgical procedures for advanced cancer, 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 have 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.
Interferon has not been widely used because it is______.
选项 A、still very dangerous
B、not yet available in the United States
C、difficult to produce in large quantities
D、not effective for human beings
答案C
解析 第一段，作者指出“全世界去年才生产出一克干扰素”，第二段接着又谈到干扰素的缺乏(scarcity)，第四段指出干扰素在治疗癌症方面，非常有效，因此选项D不正确，文中第一段也已谈到the new drug has provoked no negative reaction of sufficient significanceto discourage its use“还未发现该药物有什么副作用”，因此选项A也不正确，综合判断得出，不能投入大量生产才是导致干扰素不能被广泛应用的原因。选项C正确。
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