September 4, 2008: Using a new technology, called a multi-trap nanophysiometer, scientists at the Vanderbilt Institute for Integrative Biosystems Research and Education have detected previously unnoticed chemical signals that individual cells in the immune system use to communicate with each other over short distances. This is one of the first microfluidic devices that has been applied successfully to the study of cell-to-cell signaling in the immune system.
The signals the researchers detected originated in dendritic cells — the sentinels of the immune system that do the initial detection of microscopic invaders — and were received by nearby T-cells, which play a number of crucial roles in the immune system, including coordination of attacks on agents that cause disease or infection.
A detailed description of the multi-trap nanophysiometer (MTN) and how it enabled the accidental discovery of paracrine signaling has been published online by the journal Lab on a Chip. The new device was developed by a team of researchers headed by John P. Wikswo, the Gordon A. Cain University Professor at Vanderbilt.
Director John Wikswo sitting in front of a multi-trap nanophysiometer (Source: Vanderbilt)
“This is an important advance and potentially very useful technology,” says co-author Derya Unutmaz, an associate professor of microbiology at New York U.’s School of Medicine. “The ability to study the behavior of single cells may not be as critical if you are studying the heart or muscles, which are mostly formed by uniform cells, but it is crucial for understanding how the immune system functions. The wide surveillance of the body that it conducts requires extensive communication between dozens of different kinds of immune cells.”
The reason for this is that the dendritic cells, T-cells, and B-cells in the immune system, which tend to concentrate in the lymph nodes spread throughout the body, function as individual, unattached cells. If dendritic cells detect invaders in the body, they rapidly migrate to lymph nodes and have to find the appropriate T-cells to alert them. But how dendritic cells attract the right T-cells among millions of cells within the lymph nodes remains an immunological puzzle.
The MTN is the first system that can monitor biochemical changes in large numbers of normal or primary cells at the single-cell level for prolonged periods, Unutmaz says.
The new device consists of a series of hair-sized channels molded in a special kind of plastic that is glued onto the bottom of a glass microscope coverslip. A shoebox-sized pump pushes fluid (normally the media used to culture cells) through one channel that opens up into a chamber filled with hundreds of tiny, three-sided wells small enough to trap individual cells. When cells are injected upstream, they are passively trapped in the wells and are held there solely by the fluid flowing out even smaller holes in the well bottoms. By precisely controlling the flow rate, the researchers can keep normal cells alive for longer than 24 hours.
The multitrap nanophysiometer for the trapping, long-term maintenance and observation of unattached primary human immune cells. The figure shows its design, its implementation in PDMS, and sequential images demonstrating the trapping of human T cells. (Source: Lab-on-a-Chip)
The research was funded by grants from the Defense Advanced Research Projects Agency, Air Force Office of Scientific Research, the National Institutes of Health, the Vanderbilt Institute for Integrative Biosystems Research and Education and the Systems Biology and Bioengineering Undergraduate Research Experience.