Sometimes in immunology we want to know what a specific cell is doing….say a macrophage hanging out in the lung. Is it helping to calm down inflammation after an influenza infection? Is it making inflammation worse? Is it talking to other immune cells after a transplant? Is it killing its neighbors? We may have a whole slurry of cells…T cells, B cells, macrophages, neutrophils. But we only care about what is going on with the macrophages. To figure this out we need to go from having a gigantic pool of all sorts of cells to a pure sample of only the macrophages. If we find out some information about what these specific cells are doing, maybe there is a way that we can target this cell type with drugs. “Cell sorting” is the tool we use to make a pure solution of a certain type of cell, and this Soviet-era looking equipment on the left is what helps us to do this. It’s got a pretty cool name….”MoFlo” and it’s the control center for setting everything up. The laser shown above actually does the sorting. The macrophages that we want to purify have certain molecules on their surface that are unique from the molecules on other cell types. We use colorful antibodies to bind these unique markers. You notice the thin line shooting down in the lower half of the laser picture? That’s a single stream of cells flowing through….one cell at a time. The horizontal beam of light is the laser that shines different wavelengths of light at the cells. When a cell goes through with the specific colors we are looking for, the laser detects this and the cell will be “sorted” or separated from the rest of the cells into its own tube. This colorful image below is an example of how we tell MoFlo what to do. It’s our “gating” strategy….saying we want these cells that are green a purple but not those cells that are green and red. Once cells are sorted lots of different things can be done with them including looking at what molecules they are making and incubating them with other cells to see what effect they have. And not all cell sorters are so ancient looking! Many of them look quite futuristic!