ScienceDaily (Nov. 1, 2010) — Scientists from the UK and Australia have seen the human immune system's assassin -- a protein called perforin -- in action for the first time. The UK team is based at Birkbeck College where they used powerful electron microscopes to study the mechanism that perforin uses to punch holes in rogue cells.
Model of a membrane with perforin rings allowing the passage of granzymes into the cell. (Credit: Mike Kuiper)
The research is published on October 31 in Nature.
Professor Helen Saibil, who leads the UK team at Birkbeck College, said: "Perforin is a powerful bullet in the arsenal of our immune system -- without it we could not deal with the thousands of rogue cells that turn up in our bodies through our lives."
"Perforin is our body's weapon of cleansing and death," said project leader Professor James Whisstock from Monash University, Melbourne, Australia.
Perforin works by punching holes in cells that have become cancerous or have been invaded by viruses. The holes let toxic enzymes into the cells, which then destroy them.
If perforin isn't working properly the body can't fight infected cells. And there is evidence from mouse studies that defective perforin leads to an upsurge in malignancy, particularly leukaemia, so says Professor Joe Trapani, head of the Cancer Immunology Program at the Peter MacCallum Cancer Centre in Melbourne, Australia.
The first observations that the human immune system could punch holes in target cells was made by the Nobel Laureate Jules Bordet over 110 years ago, but we have had to wait for the latest advances in structural molecular biology to find out how exactly this happens.
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