BD Accuri News

Richard Simpson on Extraterrestrial Immunology

Richard Simpson, PhD, is associate professor in the Department of Health and Human Performance at the University of Houston. His research interests focus on the effects of exercise, age, and disease on human immune function. Dr. Simpson told us about an ongoing research project, supported by NASA, examining the effects of lengthy spaceflight missions on the immune systems of astronauts. He described the challenges of working with samples from space and explained why he relies on a BD Accuri™ C6 flow cytometer in his work.

Q: Would you tell us about the research program in which you are using the BD Accuri C6?

Dr. Simpson: We’re using the BD Accuri C6 for many different projects, but one of the main projects is looking at the effects of spaceflight on the immune system of astronauts. We collect blood, saliva, and urine samples from the astronauts before they go on the International Space Station (ISS) as well as when they’re on it. The blood samples collected on the ISS get sent back down to our labs on the Soyuz space vehicle, and we process them within about 30 hours of being drawn. And then we collect several samples after the astronauts return from space so that we can look at the recovery kinetics.

The immunoassays that we’re doing include a natural killer (NK) cell function assay set up for the BD Accuri C6, looking at how well the NK cells kill many different target cells. In addition to the standard K562 [leukemia] tumor cell line, we’re looking at some transfected cell lines, cell lines of myeloma origin, and cell lines of lymphoma origin. We grow the tumor target cells in the lab, label them with CD71 (a surface marker for the transferrin receptor expressed by all tumor cells), and co-culture them with the peripheral blood mononuclear cells (PBMCs) that we get from the astronaut. Further staining with propidium iodide (PI) and labeling with CD3 and CD56 allow us to quantify both total cell death and cell death from NK cells.

We’re also doing a very comprehensive immunophenotyping analysis, looking at T-cell subsets, NK-cell subsets, neutrophils, monocytes, and B cells. We’re utilizing 4‐color flow cytometry for all this work.

Q: You said you analyze the samples within 30 hours of when they’re drawn. Do you have to draw them just before a Soyuz shuttle leaves the ISS to come back to Earth?

Dr. Simpson: That’s correct. Timing is essential. Before we started to get live samples from the astronauts, we had to do verification studies. We took blood from people in the lab and left it either in the refrigerator or at room temperature or on a rocker. We were interested in how the phenotypic and function markers change. And you would be very surprised. We were leaving blood in the lab at room temperature on a rocker up to four days, and when we did the phenotype analysis, it would look identical to fresh blood at day zero. Granted, after four days there’s a lot more debris, so you have to use the Zoom feature on the BD Accuri C6 to focus on the cells, but it works really well.

So the phenotyping can be pretty stable for several days, but to look at NK cell function, we’re really against the clock. In our stability experiments, NK functional assays on blood that was older than 40 hours did not work at all. We really have to get those blood samples back within an absolute maximum of 40 hours. But we’ve been able to do a successful NK cell functional assay with every astronaut who has come back from the space station. We also know exactly when the blood sample was drawn on the ISS. So, to adjust for sample aging, we draw a blood sample from a control subject at the exact same time. When we process them, both the astronaut sample and the control sample have aged identically.

Q: Are there any results you can share with us yet?

Dr. Simpson: So far, we have samples from two astronauts who have been in space and come back. We have seen that NK cell function tends to decrease in mid-flight with all the target cells, whether K562 or a myeloma or lymphoma cell line. It usually returns to normal levels within two weeks of returning to Earth. We also see huge composition changes in certain cell subsets. We’re putting an abstract together now.

Q: How will the results of your work be used?

Dr. Simpson: NASA wants to understand the risks associated with sending human beings on exploration-class missions to an asteroid or Mars that can take a total of 3 years. If something goes wrong, such as a medical emergency, there’s no chance of returning them to Earth. From this study of astronauts on 6-month ISS missions, we’ll try to ascertain whether there are any clinical risks associated with altered immunity. That will ultimately allow NASA to try to develop counter-measures to improve the immune system so that astronauts can embark on these long-duration spaceflight missions.

Q: Why did you choose the BD Accuri C6?

Dr. Simpson: Before I came to the University of Houston, I had worked with a BD FACSCalibur™ flow cytometer for several years. When I moved here, my startup package wasn’t large enough to afford a BD FACSCalibur, but I definitely had to do 4-color flow cytometry. At that time, the [BD] Accuri C6 was a fairly new machine. I asked one of the reps to come out and give us a demo, and I thought it looked great. Not only did it do everything I needed to do at a very good price, the interface was very straightforward and easy to work, the compensations could all be done retrospectively, and the PMTs were all fixed, so there was no real-time adjustment of PMT voltages. It ticked a lot of boxes for me and I had no hesitation in ordering one. Even though I’ve had it for over five years, it still gets me great data. The overall capabilities of the machine are simply fantastic.

It takes fairly small sample volumes as well. We’re one of many different studies that the astronauts sign up for, and pretty much every study wants blood. Since there’s only so much blood that we can take from the astronaut in space, we have to be really efficient with what we can do. For each antibody stain, we’re using 50 µL of whole blood, and that’s more than enough. Because the BD Accuri C6 collects many events from just 50 µL of blood, we can do detailed phenotyping with very limited blood volumes.

Q: What does BD Accuri’s motto, “Flow Cytometry Within Reach™,” mean to you?

Dr. Simpson: The BD Accuri C6 is very easy to operate. In the past, there was only one or two of us who had the expertise to run the samples. You couldn’t just show someone the basics and say, “I want you to put these hundred tubes through the flow cytometer.” But with the BD Accuri C6, you can show them the very basics—how to run a sample, how to save a file, how to set the machine up, how to shut it down—and they can run samples, knowing that you can go back retrospectively and reanalyze them and adjust the compensation. We get a lot more done without needing super-expert flow cytometrists to be there all the time. And the help and technical support we’ve gotten from BD has been absolutely fantastic.

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