Researchers from the University of New South Wales (UNSW) have identified the body's immunity switch for the first time by studying the inner workings of T-cells.

Katharina Gaus, study leader and associate professor in UNSW's Centre for Vascular Research at the Lowy Cancer Research Centre, along with David Williamson, a PhD candidate, and a team of researchers, have used a "super" microscope found in Australia to observe T-cell activity, which led to the discovery of the human body's immunity switch. 

T-cells are responsible for alerting our immune system when germs and other foreign entities gain access to our bloodstream. Think Paul Revere in the American Revolution, where his "midnight ride" warned patriots of the British army troops' movement just before the Battles of Lexington and Concord. By letting the immune system know to go on the defensive, our body is able to fight off some viruses and diseases. 

Researchers have wanted to know what makes T-cells spring into action, and to do so, a "super" microscope, which is capable of super-resolution fluorescence microscopy and can image a molecule as small as 10 nanometers, was required. 

Using the microscope, Gaus and her team imaged a protein, which is important in early immune response, molecule-by-molecule. By doing so, they were able to identify the body's immunity switch. 

"Previously, it was thought that T-cell signaling was initiated at the cell surface in molecular clusters that formed around the activated receptor," said Gaus. "In fact, what happens is that small membrane-enclosed sacks called vesicles inside the cell travel to the receptor, pick up the signal and then leave again. There is this rolling amplification. The signaling station is like a docking port or an airport with vesicles like planes landing and taking off. The process allows a few receptors to activate a cell and then trigger the entire immune response."

Researchers expect this discovery to eventually lead to treatments for a range of auto-immune diseases or even cancer.

"In conventional microscopy, all the target molecules are lit up at once and individual molecules become lost amongst their neighbors - it's like trying to follow a conversation in a crowd where everyone is talking at once," said Williamson. "With our microscope we can make the target molecules light up one at a time and precisely determine their location while their neighbors remain dark. This 'role call' of all the target molecules means we can then build a 'super resolution' image of the sample."

The researchers plan to continue their studies by working to pinpoint other key proteins to create a complete image of T-cell activity.