Debbie Knight

Going with the flow …

In observation on August 6, 2011 at 6:10 pm

One of the upsides (or downsides, depending on your point of view) of working for a professor who teaches is that sometimes I get asked to help. Sometimes it’s to help design a Powerpoint slide for his class presentation. But now that he’s more proficient using the program, those requests have become extremely rare.

I miss the good ol’ days when he was more of a cyberdope (his word, not mine).

Sometimes I’m recruited to help teach the first-year graduate students in his class.

This week, I got the privilege of teaching them the “mysterious” ways of flow cytometry — including how to “go with the flow.”

Here are two students watching the results come in as the sample runs through the flow cytometer

For those who are unfamiliar with flow cytometry: it is a rather complex “black box” instrument that sends cells in single file through a laser beam. And when the laser light hits the cell, several things can happen.

  • First, that light can pass pretty much straight through the cell to a detector that will relay information about the size of the cell (is it large? Is it small?) to the computer.
  • Second, the light can enter the cell, bounce off little packets within the cell called granules and hit another detector that tells the computer whether the cells has a few or a lot of those granules inside it.
  • The researcher may also be interested in whether the cell has a specific molecule on its surface or inside it and do so using special tags are placed on that molecule. Often an antibody (a protein) carrying the tag is used and that antibody then sticks to the specific molecule in or on the cell. In this case, the laser beam hits the tag, excites certain electrons in this tag, and the tag will “glow” (fluoresce, give off light). There are specific detectors that, well, detect that particular “glow” and relay the information to the computer.

Viola! Samples go into the "black box" and data comes out on the computer screen

As far as teaching the students goes, it is more of an introduction to flow cytometry than a detailed how-to. They tag a few different molecules on the outside of the cell. The “exciting” part, pardon the pun, is when they run the cells through the instrument.

The part I find most amazing is that within a few seconds, the instrument has looked at over 5,000 cells and told them quite a bit of information about each and every one of those cells. If they had to look at 5,000 cells under the microscope, count them, determine if the cell has a tag on it or not (and how much of the tag), it would take them much longer than the fifteen seconds the flow cytometer does it.

The flow cytometer can show the size and granularity of the cells, how much of a fluorescent tag is present on the cells, and much more. Here, 5,000 cells were examined in 15 seconds!

I cover this in a bit more detail with the students — including showing them what’s inside the “black box” — but I think this gives you the idea.

The first day of teaching, the software on the instrument we were supposed to use disappeared. This meant we had to come up with a plan B — i.e., find another flow cytometer. We scrambled, but managed to find one we could use for the morning.  We had less than 30 minutes  to rebuild the template and tweak the detectors before the students started coming. Yikes!

I thought to myself THIS must be what they mean by “going with flow.”

Despite the initial technical difficulties, the students seemed genuinely interested in learning the “mysterious” ways of flow cytometry. And as I was able to answer most of their questions., I felt I had dispelled some of that mystery.But maybe that’s just me, learning to “go with the flow.”

  1. This story was highlighted on Chromocyte News today. Thanks, Chromocyte!

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