For the first time on the screen: the deadly battle of a leukocyte with a microbe

DailyTechInfo based on Gizmag: Time-lapse captures the death of white blood cells for the first timeThe main defense mechanism of our body, reflecting the "attack" of infections and pathogens, is its immune system.

And the main role in the immune system is played by leukocytes, white blood cells, which are "weapons" that attack invading microorganisms and viruses. Until recently, scientists have studied the principles of the immune system and the functioning of leukocytes quite well, the subtleties of the final moment when the leukocyte cell dies as a result of the fight against the disease remained insufficiently studied. And recently, a group of Australian scientists made a detailed high-quality video recording of the death of a leukocyte, whose cell, when destroyed, emits proteins of a certain type and the remnants of its contents into the environment.

It is likely that such consequences of the death of a leukocyte cell are a kind of signal warning other leukocytes nearby about the presence of pathogens in this area. And a thorough study of this mechanism can serve as the basis for completely new methods of treating infectious diseases, for the development of new drugs, etc.

"The role of white blood cells in the immune system of our body is the most important. These white cells take the first blows of infection and very often die, throwing out molecules of certain proteins into the surrounding space, just as a downed fighter jet throws out its pilot with a catapult. At the same time, the "signal" proteins spread over sufficiently long distances, while others that do not matter remain near the site of cell death," says Dr. Ivan Poon from the School of Molecular Sciences at La Trobe University, Melbourne.

Dr. Poon's group worked together with scientists from the University of Virginia in the direction of leukocyte research. In these studies, scientists used microscopy technology (time-lapse microscopy), in which a camera mounted in a microscope takes pictures at certain time intervals and based on these images, a video is later mounted.

What the scientists managed to see on the video they received was a complete surprise for them. It turns out that the process of leukocyte death occurs in a much more orderly manner than previously thought. The proteins used to transmit signals are arranged in a certain order inside the dying cell, which increases in size until its membrane ruptures, shooting into the space of a "necklace" of proteins.

A picture from the press release of La Trobe University Human cell death captured for the first time – VM.

Scientists have called the chains of signaling proteins the term "beaded apoptodia", and their length is eight times the size of the cell inside which they were until the last moment. Although scientists are already guessing about the functions of these proteins, all this remains only an assumption. The first assumption is that these proteins play the role of a signaling system that notifies neighboring leukocytes of the presence of pathogens. The second assumption is more exotic, according to him, protein strands are the ways in which a virus or a bacterium can easily move to another part of the body, where they are waiting for fresh leukocytes ready for battle.

"This was the first time in history when we saw firsthand all the subtleties of the processes taking place," says Dr. Poon. – "When we understand the causes and consequences of this behavior of dying white cells, we will be able to develop treatment methods based not on drugs, but on the activation of our own immune system, which, in our opinion In my opinion, it will be both more effective and safer for patients."

Article by Atkin-Smith et al. A novel mechanism of generating extracellular vesicles during apoptosis via a beads-on-a-string membrane structure is published in open access in the journal Nature Communications – VM.

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22.06.2015