雅思阅读 113: Pig Kidneys and the Quest for Unlimited Organs（猪肾与无限器官的追求）

改编自 Harvard Medical School / Mass General Communications（2025年2月）。雅思阅读 Section 3 难度，约 1050 词。 素材来源：https://hms.harvard.edu/news/surgeons-perform-second-pig-kidney-transplant-massachusetts-general-hospital

Reading Passage

A. Every year, thousands of people die waiting for an organ that never arrives. In the United States alone, more than a hundred thousand patients are on the transplant waiting list, and roughly seventeen of them perish each day while their names remain on it. For kidneys, the shortage is particularly severe: around ninety thousand Americans were waiting for a donor kidney as of late 2024, yet transplanting one into the right recipient requires a scarce match between two strangers. The problem is not that medicine cannot replace a failing kidney. It is that the supply of healthy organs, donated by living volunteers or harvested after death, simply cannot meet the demand. Dialysis keeps many patients alive, but it is a burdensome, debilitating treatment that raises the risk of heart complications and infection while eroding quality of life, and it cannot restore the body's natural balance of fluids and hormones. For decades, surgeons and geneticists have dreamed of a way out: grow organs in animals, make them compatible with humans, and transplant them on demand rather than waiting for a stranger's gift. That idea, once dismissed as science fiction, has moved decisively into operating theatres in the last two years, funded by a handful of biotechnology firms and watched by every patient on a waiting list.

B. The animal chosen for this experiment is the pig. Pigs are not a random favourite. Their kidneys are similar in size to human ones, they breed quickly, and their physiology is close enough to ours that a transplanted organ might plausibly perform the same job. Yet for all that, transplanting a pig kidney into a human seemed for decades almost impossibly dangerous. Two barriers stood in the way. The first is the immune system, which would immediately recognise the pig organ as foreign and attack it. The second is subtler and more insidious: the pig genome carries embedded viruses, known as porcine endogenous retroviruses, that could, in theory, jump into the human recipient and cause new infections. Both problems have been tackled with CRISPR gene editing. A company called eGenesis, co-founded by the geneticist George Church, engineered pigs whose organs carried sixty-nine genetic modifications. Some edits switched off pig genes that trigger violent immune rejection; others inserted human genes to smooth the organ's behaviour; a third set permanently disabled the embedded viruses, removing the zoonotic risk at its source.

C. The first such operation took place at Massachusetts General Hospital in March 2024, when a gene-edited pig kidney was placed into a sixty-two-year-old man with end-stage kidney disease. It was followed, on 25 January 2025, by a second procedure on Tim Andrews, a sixty-six-year-old patient from New Hampshire who had endured dialysis for more than two years and had already suffered a heart attack. Blood type complicated his search: patients with O-group blood, who can donate universally, are among the hardest to receive an organ themselves, often waiting five to ten years instead of the usual three to five. Discharged within a week of surgery, Andrews stepped off dialysis for the first time in years, his new kidney working as expected. His case, however, was not without a cautionary note. The world's first pig-kidney recipient had died roughly two months after his operation, not because the organ failed but from an unrelated cardiac event. Doctors emphasised that the early operations were performed under a special regulatory pathway reserved for desperate patients, and that they were not yet proof of routine, safe, long-term replacement.

D. Even when a pig kidney starts working, the human immune system does not quietly accept it. In the first recipient, surgeons observed an early episode of T-cell-mediated rejection — the targeted aggression of immune cells against the new tissue — which they managed to reverse with a potent antibody drug, thymoglobulin. The episode exposed a truth that no amount of editing can yet erase: cross-species transplantation demands immune-suppressing medicines that are heavier, and less forgiving, than those used between two humans. Recipients face the usual transplant risks — infection, organ damage, drug side effects — multiplied by the gap between species. That gap also makes surveillance harder. Every animal virus, no matter how thoroughly screened, must be watched for in the recipient long after the incision heals. Researchers caution that what looks like success in a handful of patients may conceal problems that only surface with larger numbers and longer follow-up. Optimism, on the surgical team's own account, is qualified rather than unbounded.

E. By late 2025, the field had outgrown its handful of heroic one-off cases. In November that year, a separate team at New York University performed the first transplant under a formal, FDA-approved clinical trial, using a pig kidney engineered with ten genetic modifications rather than sixty-nine — evidence that engineers were still arguing over exactly how many edits are necessary. The American regulator had earlier cleared the way for broader trials of the sixty-nine-edit organ, marking the moment xenotransplantation stopped being a curiosity for journalists and became a regulated medical product. Supporters argue that, if perfected, animal organs could eventually abolish the waiting list entirely, offering a plentiful, manufactured supply to patients like Andrews who would otherwise spend years tied to a dialysis machine. Critics, however, point to the unresolved biology — the rejection, the surveillance burden, the possibility of viruses crossing species — and to the ethical questions of breeding and sacrificing animals for human parts. Whether pig organs become routine treatment or remain a narrow experimental option is, for now, an open question written in the tissue of a few brave recipients. Each operation adds a data point — a survival time, a rejection episode, a side effect — and only when enough such points accumulate will surgeons know whether the 69-edit organ is the right design, an over-engineered one, or merely the first of many.

Questions 1-4

Choose the correct heading for paragraphs B, C, D and E from the list of headings below.

List of Headings i. Why pigs — and how genetics solved two ancient problems ii. The cost of dialysis in the United States iii. The early human recipients and their mixed outcomes iv. The immune system's lingering war against the transplant v. From one-off surgeries to formal clinical trials vi. How CRISPR was invented in the 1980s vii. The history of animal husbandry

1. Paragraph B: ____
2. Paragraph C: ____
3. Paragraph D: ____
4. Paragraph E: ____

Questions 5-8

Choose the correct letter, A, B, C or D.

5. Why are pigs considered suitable donors? A. Their organs are identical in every way to human organs. B. Their kidneys are comparable in size and their physiology is close to ours. C. They carry no embedded viruses at all. D. They cannot be bred in captivity.

6. What did the sixty-nine genetic modifications achieve? A. They made the pig itself larger and stronger. B. They switched off rejection-triggering pig genes, added human genes and disabled embedded viruses. C. They allowed the kidney to grow inside the human body. D. They replaced the pig's entire genome with a human one.

7. Why was Tim Andrews's search for a human kidney especially difficult? A. He was too old to be listed. B. His O-group blood type restricted who could donate to him. C. He refused dialysis. D. He lived outside the United States.

8. How did the surgeons respond to the early T-cell rejection episode? A. They removed the transplant immediately. B. They reversed it using an antibody drug. C. They ignored it because it was harmless. D. They replaced the kidney with a second pig organ.

Questions 9-13

Do the following statements agree with the claims of the writer?

Write:

• TRUE if the statement agrees with the information
• FALSE if the statement contradicts the information
• NOT GIVEN if there is no information on this

9. Dialysis is a treatment that carries cardiovascular risks and infections.
10. The first pig-kidney recipient died because the transplanted organ failed.
11. Patients with O-group blood type typically wait a shorter time for a kidney.
12. The NYU trial kidney used the same number of genetic modifications as the Mass General organ.
13. All recipients of pig kidneys have completely recovered without any medication.

Questions 14-15

Complete the summary below using NO MORE THAN TWO WORDS from the passage.

The pig genome carries embedded viruses called porcine endogenous (14) __________, which the gene edits permanently disabled to remove the risk of (15) __________ crossing into the recipient.

答案与解析

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