A few weeks ago I posted about research I am doing while abroad at the Walter and Eliza Hall Institute of Medical Research (left). This research aims to understand how dendritic cells, an immune system cell type principally responsible for presenting antigen to other cell types, influence the induction of regulatory T cells in mice. Our first experiment took about three weeks to complete and lead to some intriguing results while also revealing some difficulties with our experimental design. These difficulties must be eliminated before we can be sure our results are real. Each experiment consists of about one hundred different cell cultures that must be analyzed, and since this was the first time this particular experiment has been carried out, it is not surprising that our results were somewhat ambiguous.
So, as is not altogether uncommon in science, we are repeating the experiment. But this time we are using a strain of mice with a different immunological background, something that can affect the way these mice’s cells grow in culture and interact with the antibodies we use to distinguish them. Therefore we are hoping this new experiment will either validate or disprove the results of our previous experiment.
These cell cultures are set up with the help of fluorescence-activated cell sorting flow cytometry. FACS machines, somewhat more sophisticated than their homophonic counterparts, work by detecting fluorescent markers on the surface of cells and then applying different charges to each of these cells according to which markers are attached to them. These cells then travel one by one through an electrostatic deflection system that diverts differently marked cells into different collection tubes, physically separating them from what was a heterogeneous mixture. Some of these FACS machines are capable of sorting thousands of cells per second with very little error, applying different charges to each cell for time intervals that are hard to imagine. Without these machines experiments like the ones we have been doing would be many times more tedious and perhaps impossible.