The Big IF in Cancer

  • Share
  • Read Later

(5 of 11)

Baron was one of the few to persevere. He and other interferon researchers had little to go on, for there was practically no interferon available to be studied. The chemical is produced only in minute quantities in living cells, and extracting it proved difficult and costly, liabilities that are only now beginning to be overcome. Also, though all vertebrate animals produce IF, it seems to be species specific, meaning that it works only in the type of animal that produces it. Monkey interferon works only in monkeys, mouse in mice and human in humans. Thus, unlike the insulin extracted from cattle and pig glands and used by humans, IF harvested from animals does not work in people. Lindenmann continued working with IF for about three years, but then left it, believing its puzzles could best be worked out by biochemists. "I spared myself years of frustration," he says. Most of his colleagues, aware of the difficulties of interferon studies, considered his decision totally rational. Said one distinguished virologist at the time: "Anybody who abandons interferon research cannot be entirely stupid."

Throughout most of the 1960s, a handful of interferon enthusiasts continued working with only the tiniest amounts of material, gradually unlocking interferon's secrets. They found that it is a protein produced by cells in response to some stimulation, usually by a virus. To date, at least three varieties of IF have been identified. One kind is produced by leukocytes, or white blood cells. A second type is generated by fibroblasts, cells that form connective tissue in skin and other organs. (A prime source of fibroblast IF is the foreskin of circumcised infants.) The third, called immune interferon, is apparently made by T lymphocytes, soldier cells that attack invaders and are part of the body's immune system.* Each seems to work best in protecting cells similar to those that produced it.

The mechanism of IF's defense against viruses has also emerged. Explains Mathilde Krim, a researcher at Manhattan's Memorial Sloan-Kettering Cancer Center: "Interferon is a kind of chemical Paul Revere." When a virus invades a cell, instead of turning out the proteins needed to sustain the cell and other parts of the body, the manufacturing plant begins to produce carbon copies of the virus. Eventually bloated with the alien bodies, the cell almost literally comes apart at the seams and dies, spilling out its cargo of new viruses, which promptly move toward healthy cells to repeat the process and spread the infection.

Enter interferon. The initial infection somehow triggers the first cell into producing IF. In turn, the interferon assumes the role of an intercellular messenger; it passes through the cell membrane and moves on to warn surrounding cells of the viral invasion. The healthy cells respond by producing antiviral proteins, which meet any invader head on. The entering virus will not be able to replicate within the new cell; if it does manage to reproduce, its progeny find that they are unable to leave the cell. The cycle of infection is broken.

  1. 1
  2. 2
  3. 3
  4. 4
  5. 5
  6. 6
  7. 7
  8. 8
  9. 9
  10. 10
  11. 11