Filming How Our Immune System Kills Bacteria

hooligun shares a report from Phys.Org: To kill bacteria in the blood, our immune system relies on nanomachines that can open deadly holes in their targets. UCL scientists have now filmed these nanomachines in action, discovering a key bottleneck in the process which helps to protect our own cells. For this study, the researchers mimicked how these deadly holes are formed by the membrane attack complex (MAC) using a model bacterial surface. By tracking each step of the process, they found that shortly after each hole started to form, the process stalled, offering a reprieve for the body's own cells. The team say the process pauses as 18 copies of the same protein are needed to complete a hole. Initially, there's only one copy which inserts into the bacterial surface, after which the other copies of the protein slot into place much more rapidly.

To film the immune system in action at nanometer resolution and at a few seconds per frame, the scientists used atomic force microscopy. This type of microscopy uses an ultrafine needle to feel rather than see molecules on a surface, similar to a blind person reading Braille. The needle repeatedly scans the surface to produce an image that refreshes fast enough to track how immune proteins get together and cut into the bacterial surface. The study has been published in the journal Nature Communications.

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