After four more calls to the same company—asking various questions—McClellan reached a senior specialist who had an idea. “She said the only filter they had that might be able to go that low was an air filter, and she wasn’t sure that liquid would go through it,” he recalls. “Turns out it does—very slowly.”

About a year and a half later, McClellan’s aha moment became a fixture in his lab. “We’ve had phenomenal success using the ultrafiltered solutions with the Invitrogen Attune NxT Flow Cytometer because the equipment doesn’t require as much sheath fluid as other flow cytometers, shortening the time needed to do the filtering,” he says.

“When ultrafiltering first started to work, I wondered, ‘Why isn’t everyone doing this?’” McClellan continues. “They probably tried to but were told they couldn’t. Luckily, I don’t take no for an answer.”

McClellan’s flow cytometry training began when he was a University of Florida medical technology student. Dr. Raul Braylan—McClellan’s mentor at the time and now a senior clinician at the NIH—told him that mastering the technology, which was relatively new at the time, would mean he’d always have a job. “He was right,” McClellan acknowledges. “I’ve worked in a variety of areas, from stem cell therapy and diabetes to transplant immunology and xenotransplantation. Through it all I’ve always been “the flow guy”.”

McClellan has given back to the flow cytometry field as much as he’s gotten from it. He cofounded the SouthEast Flow Cytometry Interest Group (SEFCIG), a regional organization of “cytoflow geeks” who gather every year to talk shop, he says. “Cytometry is a unique discipline in that I know of no other technology that has garnered such a close-knit group of users,” McClellan says, adding that the regional groups are important because it gets harder to travel to ISAC—the annual international flow cytometry meeting—as university budgets get smaller. “The group also fosters a sense of comradery that’s sorely lacking in science these days.”

It’s that comradery, not to mention curiosity, that McClellan tries to pass along to the next generation of scientists. “It is imperative that we foster interest in science among our youth,” he stresses. “I coordinate all of the high school and undergraduate students that volunteer at MCI to gain experience in the research labs. As a scientific discipline, it is also important for us as flow cytometry professionals to nurture and develop the next generation of flow guys and girls.”