09-14-2011, 08:35 AM
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Cancer Killing Cells Caught On Camera
| |Cancer killing cells have been caught on camera - in 3D and in more detail than ever before.
A team of British scientists used optical laser tweezers and a powerful microscope to analyse the inner workings of the cells.
It revealed, in the highest ever resolution, how white blood cells destroy diseased tissue using 'deadly granules'.
Professor Daniel Davis, of Imperial College London, said: 'Actually seeing what is going on in our bodies in such minute detail is a very big deal.
'You cannot gain this knowledge any other way. You can read all about individual genes and molecules and what is supposed to happen but there is nothing as rewarding as this.
'Just like astronomers are building bigger and better telescopes to peer into the depths of space, we are developing ever more powerful microscopes to view things at the quantum level.'
The study looked at a type of white blood cell, called a Natural Killer (NK) cell, that protects the body by identifying and killing diseased tissue.
It showed how white blood cells rearrange a scaffolding of proteins on the inside of its membrane to create a hole through which it delivers the deadly enzyme-filled granules to kill diseased tissue.
Prof Davis added: 'NK cells are important in our immune response to viruses and rogue tissues like tumours.
'They may also play a role in the outcome of bone marrow transplants by determining whether a recipient's body rejects or accepts the donated tissue.'
It is hoped that learning how NK cells identify which tissues to kill, could lead to better health care for some patients.
'In the future, drugs that influence where and when NK cells kill could be included in medical treatments, such as the targeted killing of tumours,' he added.
'They may also prove useful in preventing the unwanted destruction by NK cells that may occur in transplant rejection or some auto-immune diseases.'
Physicists at Imperial used a super high-resolution microscope from the University of Oxford to see the new visual resolution of NK cell action.
The researchers immobilised an NK cell and its target using a pair of 'optical' laser tweezers so that the microscope could capture all the action at the interface between the cells.
They then watched inside the NK cell as proteins parted to create a tiny portal and the enzyme-filled granules moved to it, ready to pass out of the NK cell and onto the target to kill it.
Dr Alice Brown said: 'These previously undetectable events inside cells have never been seen in such high resolution. It is truly exciting to observe what happens when an NK cell springs into action.'
The contact between an NK cell and its target is only about a hundredth of a millimetre across and the minuscule proteins, known as actins, and granules change position continuously over the few minutes from initial contact until the target is killed.
The microscope has to be able to capture images quickly enough and in high enough visual detail in order to reveal their activity.
Most microscopes view images in the horizontal plane.
And so to view an interface between two cells at any other orientation would require 'stacks' of multiple horizontal images combined to make a 3D image.
This significantly limits the speed at which cell dynamics can be viewed and reduces image quality.
Prof Paul French, of Imperial College London who helped develop the microscopy, said: 'Using laser tweezers to manipulate the interface between live cells into a horizontal orientation means our microscope can take many images of the cell contact interface in rapid succession.
'This has provided an unprecedented means to directly see dynamic molecular processes that go on between live cells.'
Professor Ilan Davis, of the University of Oxford, whose group applies super resolution technique to basic cell biology research, said: 'Our microscope has given us unprecedented views inside living NK cells capturing a super-resolution 3D image of the cell structures at twice the normal resolution of conventional light microscope.
'This method, developed at University of California San Francisco by Professor John Sedat, maximizes the amount of light captured from the specimen while minimizing the amount of stray light inside the instrument.'