Superresolution fluorescence microscopy has provided a glimpse into the inner workings of T cells, the front-line troops that alert our immune system to go on the defensive against germs and other invaders in our bloodstream. The discovery identified the exact molecular switch that spurs T cells into action — a breakthrough that could lead to treatments for conditions ranging from autoimmune diseases to cancer. Studying a cell protein that is important in early immune response, researchers at the University of New South Wales (UNSW) used Australia’s only superresolution fluorescence microscope to image the protein molecule by molecule to reveal the immunity switch. “Previously, you could see T cells under a microscope, but you couldn’t see what their individual molecules were doing,” said associate professor Katharina Gaus. Using the new microscope, the scientists imaged molecules as small as 10 nm. Gaus said that what the team found overturns the existing understanding of T cell activation. “Previously, it was thought that T cell signaling was initiated at the cell surface in molecular clusters that formed around the activated receptor,” she said. “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.” Gaus said the discovery explains how the immune response could occur so quickly. “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,” she said. For more information, visit: www.unsw.edu.au