Take a look at how immune cells dig tunnels in tissues

Two orbital overlapping immune cell images: Sadjadi and others
Recently, researchers reported in the journal
of Cell Press that a type of white blood cell called cytotoxic T lymphocytes (CTL) can tunnel in tissues, potentially allowing other CTLs to reach infected and tumor cells quickly. The results showed that some CTLs move slowly as they create channels through the extracellular substring (ECM), the main component of the tissue. Other CTLs then pass through these channels quickly, presumably to effectively search for and remove target cells.
"It has not been clear how immune cells migrate and their search strategies in extracellular substrings, and there is a greater interest in physics and biology at the moment." "Our findings suggest that the regulatory properties of tissue ECM will have an impact on the efficiency of the immune response and may lead to new treatment strategies for cancer treatment," said senior study author Heiko Rieger of the University of Saar. CTL
key role in removing pathogen-infected and tumor cells. In order to find their targets, they must navigate and migrate in complex bio-micro-environments, which are shaped by ECMs. The number of these target cells is usually low in the early stages of disease development, so CTL's ability to quickly find these target cells is critical to an effective immune response.
ECM is mainly composed of collagen and plays an important role in almost all cellular functions. In all types of cancer, collagen networks become dense, stiff, and highly arranged near tumors, facilitating the transport of cancer cells and enabling ECM to play an important role in cancer metastasis, invasion and prognosmation. "Understanding the migration and interaction of immune cells in collagen networks is critical to unlocking the underlying details of the immune response and designing effective treatment strategies." Rieger said.
To solve this problem, researchers at the University of Saarra used a 3D network to simulate ECMs of different concentrations of bovine collagen, and used 3D live cell imaging from a photoscopic microscope to analyze the migration trajectory of human CTL in the substation. CTL shows three different types of motion: slow, fast, and mixed. Mathematical models built by Zeinab Sadjadi, the paper's first author, show that cells move between fast and slow states.
the presence of target cells, natural killer (NK) cells in collagen have similar types of motion. NK cells have immune function similar to CTL. "The similarity of the characteristics of the movement trajectory of CTL and NK cells indicates a common mechanism for the migration of two cells through collagen networks." Rieger said.
based on the initial findings, the researchers hypothesically assume that CTL moves slowly because they push open and tear collagen fibers to form channels that promote the rapid movement of other T cells in the collagen network. Experimental evidence supports this hypothesis. For example, migrating T-cells move back and forth in exactly the same orbit, and they move quickly in channel-like voids in collagen substations.
limitation of this study is that it uses a synthetic collagen substitin. But living tissue contains many other components that may affect immune cell migration behavior.
next step, the researchers plan to analyze the long-term effects of T-cells on ECM. They will also study whether these channels enhance CTL's ability to find target cells in collagen substrings. "Understanding how CTL migrates in these tissues may lead to new treatment strategies to prevent early cancer metastasis," Rieger said. (Source: Lu Yi, China Science Journal)
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