For the first time on the screen: neutrophils are on the trail
Scientists at Yale University, working under the leadership of Eric Dufresne and Holger Kress, have developed a new method for studying the interaction between the immune cells of our body and bacteria.
When bacteria enter the body, they begin to secrete certain molecules, leaving behind a kind of chemical trace. Experts know that the cells of the immune system use these traces to detect bacteria. However, studying the mechanisms by which immune cells process such chemical signals has so far been very difficult.
The authors have developed a method for creating artificial chemical signal sources that can be moved in three dimensions. This allowed scientists to direct the movement of neutrophils – one of the types of immune blood cells – in the desired direction and study the mechanisms of their response to these signals.
The paper used spongy microparticles developed by the laboratory of Tarek Fahmy, also from Yale University. Mimicking bacteria, these particles slowly released a chemical "smell" characteristic of bacteria. By moving these microparticles with the help of focused light rays (optical tweezers), the authors controlled the shape of the cloud of released molecules in time and space, thus stimulating the reactions of immune cells.
To demonstrate the possibilities of controlling the movement of neutrophils, two different compounds were used in the work, one of which attracted neutrophils, and the second repelled them. As a result, the authors managed to capture cells moving towards microparticles, as well as trying to avoid collisions with them. They also had the opportunity to study the nature of the response of cells to conflicting signals released by various "pseudo-bacteria".
The video on the Yale University website shows very well (unfortunately, not for long – the three-minute shooting was accelerated so that it takes five seconds) how the neutrophil is chasing a "delicious-smelling" microparticle, which the researchers move with optical tweezers. This and 7 more videos can be viewed in additional materials to the article "Cell stimulation with optically manipulated microsources", published on November 15 in the preliminary on-line version of the journal Nature Methods.
Chemotaxis, the migration of cells towards chemical signals in their microenvironment, underlies a number of important biological processes, one of which is the formation of immune responses. According to Kress, understanding the mechanisms underlying the response of cells to chemical stimuli will allow researchers to better understand how a fertilized egg turns into a complex organism, how the brain cells of an embryo form a complex network of neurons and how malignant cells spread throughout the body. The new technique will also give biologists the opportunity to study in more detail the mechanisms of response of various cell types to environmental stimuli in a variety of situations.
Evgeniya Ryabtseva
Portal "Eternal youth" http://vechnayamolodost.ru based on materials from Yale University: Scientists Guide Immune Cells with Light and Microparticles.
23.11.2009