AsianScientist (Aug. 25, 2017) – In a study published in the journal Scientific Reports, scientists in Japan have made quantitative observations of how the movement of surface molecules enables T-cells to enact an immune response to infection.
To kill a pathogen invading the human body, immune cells called T-cells bind to foreign bodies using T-cell receptors (TCR). One of the first events this binding is the formation of a microcluster that includes tens or hundreds of TCR molecules. These microclusters are deemed essential to initiate and sustain the immune signal.
In this study, the team of scientists led by Professor Makio Tokunaga at the Tokyo Institute of Technonology used a data analysis technique known as moving subtrajectory (MST) analysis to define the dynamics and kinetics of key surface molecules in T-cells during an infection.
“Imaging technologies have been used to visualize the generation and dynamics of microclusters, but there is no quantitative data. We developed this MST analysis tool using single-molecule tracking to quantitatively study the dynamics and kinetics of CD3 and CD45 around TCR microclusters,” explained Tokunaga.
Assistant Professor Yuma Ito of Tokyo Institute of Technology explained that MST analysis reveals details on the temporal and spatial variation of CD3 and CD45 movement, making it superior to standard analysis methods.
“Standard methods analyze the mean square displacement of the whole trajectory. MST divides the trajectory into subtrajectories and calculates the mean square displacement of each subtrajectory. Using MST, we could analyze movement inside, outside and at the boundary of the TCR microclusters,” said Ito.
The researchers found that the dynamics of the two molecules depended on their location relative to the microclusters and could be used to determine how they interact with the microclusters. Data from measurements of molecular kinetics further showed that CD3 and CD45 could take either a fast or slow mobility state.
Inside the microcluster, the slow mobility state was dominant, reflecting stronger interactions between the two molecules and the microcluster. On the other hand, when CD3 and CD45 were located on or outside the boundary of the microcluster, the fast mobility state was dominant. Notably, the researchers also found evidence of TCR nanoclusters beyond the boundary of the microclusters.
“The appearance of nanoclusters gives us a new understanding of the dynamics of microclusters. The dynamics and kinetics at the single molecule level is very important for defining the molecular mechanisms of biological functions,” said Tokugawa.
“Along with the new development of biopharmaceuticals related to immune control, the elucidation of the mechanism of T-cell activation is becoming more important in clinical application. Detailed quantitative data will assist in the manufacturing of biopharmaceuticals with stronger effects on the immune system.”
While this paper demonstrates the application of MST analysis to TCR microclusters, the technique is also applicable to any cellular complex that depends on spatiotemporal dynamics, the authors said.
The article can be found at: Ito et al. (2017) Multi-color Single-molecule Tracking and Subtrajectory Analysis for Quantification of Spatiotemporal Dynamics and Kinetics upon T cell Activation.
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Source: Tokyo Institute of Technology.
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