Immune system defence force captured in action

How the natural defence force within our immune system attacks and destroys harmful invaders such as virus-infected and cancerous cells has been visualised in microscopic detail by scientists from UCL, Birkbeck, University of London, Peter MacCallum Cancer Centre and Monash University, Australia. The research, published today , deepens understanding of the critical role of the protein called 'perforin' in a functioning immune system, bringing us one step closer to new therapies with the potential to boost or inhibit its impact when required. Professor Bart Hoogenboom (UCL Physics & Astronomy and London Centre for Nanotechnology) and Professor Helen Saibil (Birkbeck, University of London) used atomic force microscopy and electron microscopy to reveal precisely how a subset of white blood cells, called cytotoxic lymphocytes (or Killer T'Cells), show remarkable efficiency in first perforating their victims and next injecting poisonous enzymes to rid the body of disease. Using a form of microscopic CCTV, it was shown how perforin binds to the protective membrane that surrounds harmful cells. Professor Hoogenboom said: 'Our immune system needs to drill holes in virus-infected and cancerous cells to get rid of them, but can't buy such drills in a DIY shop. We have now shown how it self-assembles these drills on the spot by putting multiple perforin molecules together in ring-like structures, leaving tiny holes - just tens of nanometres in diameter.' Associate Professor Ilia Voskoboinik, a lead co-author (Peter MacCallum Cancer Centre), said: 'To kill virus-infected or cancerous cells, perforin must be quick and efficient.