Clipping Board » New Knowledge and the Unknown of Life ─ Life will always bring you surprises and wonders.
Update Date: 2009/01/12 08:20 Liu Xueyuan
(AFP, Paris, 11th)
American scientists have discovered that Natural Killer (NK) cells, previously considered a blunt weapon of the immune system against microbes, are actually quite sophisticated and possess the ability to remember past invaders. This astonishing discovery about NK cells may open new avenues for vaccine research.
Previously, Natural Killer cells were classified as part of the innate immune system. In terms of human evolution, the innate immune system is seen as an ancient, basic response system. It treats each infection as a completely new invasion.
NK cells are responsible for destroying infected cells, activated by distress signals called cytokines released by the cells.
Another immune system is known as the adaptive immune system, which includes lymphocytes named B and T cells, possessing "immune memory," meaning they can remember returning invaders.
Vaccines work by utilizing this immune memory. By introducing disabled pathogens (or their fragments) into the body, the adaptive immune system can learn to recognize and destroy the same invaders years or even decades later.
In a study published online by the British scientific journal "Nature," a research team led by microbiologist Lewis Lanier from the University of California, San Francisco, infected laboratory mice with Cytomegalovirus.
The researchers examined the NK cells of the infected mice and found their surfaces covered with receptors that allow them to target virus-infected cells. The researchers observed these marked cells over the following weeks and months and re-examined the infected mice.
After infection, some NK cells hid in the lymphatic tissues, mimicking the lymphocytes of the adaptive immune system, to respond more quickly and effectively when the virus returns.
The researchers transplanted some of these "memory" cells into uninfected mice and then exposed the mice to the same virus. Within less than a week, a large number of specific virus NK cells appeared in these mice, protecting them against the disease.
The study suggests that existing thinking about NK cells should be "completely revised" due to this discovery.
NK cells seem to possess characteristics of both the innate and adaptive immune systems. Lanier told AFP, "This changes the existing mindset." Lanier added, "It also opens up the question of whether it is possible to actually vaccinate NK cells as well as B and T cells against infectious diseases such as AIDS."
Previous research has found that some people have stronger resistance to HIV, taking a longer time to develop the disease after infection.
Part of the findings of this new study suggest that this difference may be partly due to some people's unique NK receptors being more effective against HIV-infected cells. But so far, this is only statistical evidence, not direct evidence.
Lanier said, "If we can figure out these specific NK cells, perhaps we can enhance their activity and more easily control the virus."
Source: http:/ / tw. news. yahoo. com/ art……url/ d/ a/ 090112/ 19/ 1ctd7. html
Surprising Immune Discovery: Natural Killer Cells Possess Memory
(AFP, Paris, 11th)
American scientists have discovered that Natural Killer (NK) cells, previously considered a blunt weapon of the immune system against microbes, are actually quite sophisticated and possess the ability to remember past invaders. This astonishing discovery about NK cells may open new avenues for vaccine research.
Previously, Natural Killer cells were classified as part of the innate immune system. In terms of human evolution, the innate immune system is seen as an ancient, basic response system. It treats each infection as a completely new invasion.
NK cells are responsible for destroying infected cells, activated by distress signals called cytokines released by the cells.
Another immune system is known as the adaptive immune system, which includes lymphocytes named B and T cells, possessing "immune memory," meaning they can remember returning invaders.
Vaccines work by utilizing this immune memory. By introducing disabled pathogens (or their fragments) into the body, the adaptive immune system can learn to recognize and destroy the same invaders years or even decades later.
In a study published online by the British scientific journal "Nature," a research team led by microbiologist Lewis Lanier from the University of California, San Francisco, infected laboratory mice with Cytomegalovirus.
The researchers examined the NK cells of the infected mice and found their surfaces covered with receptors that allow them to target virus-infected cells. The researchers observed these marked cells over the following weeks and months and re-examined the infected mice.
After infection, some NK cells hid in the lymphatic tissues, mimicking the lymphocytes of the adaptive immune system, to respond more quickly and effectively when the virus returns.
The researchers transplanted some of these "memory" cells into uninfected mice and then exposed the mice to the same virus. Within less than a week, a large number of specific virus NK cells appeared in these mice, protecting them against the disease.
The study suggests that existing thinking about NK cells should be "completely revised" due to this discovery.
NK cells seem to possess characteristics of both the innate and adaptive immune systems. Lanier told AFP, "This changes the existing mindset." Lanier added, "It also opens up the question of whether it is possible to actually vaccinate NK cells as well as B and T cells against infectious diseases such as AIDS."
Previous research has found that some people have stronger resistance to HIV, taking a longer time to develop the disease after infection.
Part of the findings of this new study suggest that this difference may be partly due to some people's unique NK receptors being more effective against HIV-infected cells. But so far, this is only statistical evidence, not direct evidence.
Lanier said, "If we can figure out these specific NK cells, perhaps we can enhance their activity and more easily control the virus."
Source: http:/ / tw. news. yahoo. com/ art……url/ d/ a/ 090112/ 19/ 1ctd7. html