A Food and Drug Administration(FDA)advisory committee has concluded that a novel new treatment can greatly help rheumatoid arthr

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问题     A Food and Drug Administration(FDA)advisory committee has concluded that a novel new treatment can greatly help rheumatoid arthritis patients.
    The panel recommended approving Enbrel for use alone in patients who haven’ t responded to other drugs or in combination with methotrexate, a cancer drug that has been the main treatment for rheumatoid arthritis.
    The FDA must make a final decision by early November, and the drug’ s maker says it could be on the market by year’ s end.
    In rheumatoid arthritis, which affects 2.1 million Americans, the immune system attacks healthy joints. A major wrongdoer in this process is a protein called "tumor killing factor" , or TNF, which interacts with a special molecule, or TNF receptor, on cells’ surfaces.
    To keep inflammation in check, cells normally release some receptors to mop up excess TNF, rendering it inactive. Apparently, rheumatoid arthritis patients don’t have enough free-floating TNF receptors.
    Enbrel consists of genetically engineered TNF receptors. In a six-month study, 234 patients with advanced rheumatoid arthritis received one of two doses of Enbrel or a placebo(harmless substance given as if it were medicine)in twice-a-week injections. They took injections for six months. By the end, 40% of patients on the larger Enbrel dose saw symptoms, such as swelling and joint pain, cut in half. Only 5% on the placebo did that well. The main side effect was minor irritation at the injection site.
    Because some TNF is needed for a normal immune response, there is at least a theoretical risk of infections or even cancer in patients who take Enbrel, so the FDA panel urged long-term safety studies.
    Last week, the FDA approved Arava, an oral treatment for rheumatoid arthritis that is similar to methotrexate. While calling both Enbrel and Arava "potentially very important" , Brian Butcher, vice president for research at the Arthritis Foundation, notes they have been tested in relatively few patients.
    Butcher says their safety should be closely monitored once they’ re widely available.
Which of the following is responsible for the inflammation of the joints?

选项 A、A special molecule on cell’ s surface.
B、A free-floating receptor.
C、A tumor-killing protein.
D、Inactive TNF.

答案C

解析 该题为细节题。由第四段第二句“A major wrongdoer inthis process is a protein called‘tumor killing factor’,or TNF…”可知,在免疫系统攻击健康关节的过程当中,主犯是一种叫做“肿瘤杀死因子”的蛋白质,它与一种特殊的分子相互作用,因此,造成关节发炎的物质是“肿瘤坏死因子”,一种杀死肿瘤的蛋白质,故选C。
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