Versiti - VBRI Welcomes Two Associate Investigators to Hematopoiesis and Immunology | Versiti Blood Research Institute

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VBRI Welcomes Two Associate Investigators to Hematopoiesis and Immunology 

Wauwatosa, WI — October 02, 2025
 

Versiti Blood Research Institute is thrilled to welcome Nicholas Jarjour, PhD, and Hongxu Xian, PhD, as associate investigators in Hematopoiesis and Immunology.  

Jarjour earned his PhD at Washington University in St. Louis and completed postdoctoral training at the University of Minnesota. His research explores the evolution of tissue-resident immunity: how immune cells (T cells and macrophages) living within organs support health, respond to disease, and adapt over time as the body changes.  

“The beauty of studying tissue-resident immune cells is that they’re the key first-responders to almost any disease process,” Jarjour says. “If we can understand how to manipulate them, maybe we can make better vaccines or make vaccines for things that are difficult to vaccinate against, like tuberculosis.”   

Jarjour is excited to start his own lab here at VBRI. “I’ve been working towards this for 15 years,” he says. “The opportunity to have an impact on other people who are training… That’s a feeling you don’t get very often. It was an easy decision to come to Versiti. The leadership and ecosystem of VBRI is a strong, stable place for the lab.”   

Xian’s first impressions of VBRI have been similar. “The people here are collaborative. They are very open and supportive,” she says. “It’s a good place to grow.” Xian grew up in China but came to VBRI from the University of California, San Diego, where she trained as a postdoctoral fellow. Prior to that, she received her PhD in cell biology at the National University of Singapore. Her research explores how mitochondrial stress activates the immune system.  

“Mitochondria aren’t just the cell’s ‘powerhouse,’” she says. “When mitochondria are stressed, their DNA becomes oxidized and act like an alarm to the immune system. If that alarm keeps ringing, it drives disease. If we figure out how to keep this oxidized mitochondrial DNA in check, we may be able to prevent or better treat autoimmune and neurodegenerative disorders.” 

When Xian reflects on her science career so far, she gives credit to the mentorship she received. “My PhD advisor, Dr. Yih-Cherng Liou in Singapore, had unwavering faith in me. He trained my critical thinking and fostered a joyful lab culture that paved my path to a postdoc with Dr. Michael Karin at UC San Diego. Karin’s relentless pursuit of rigorous, high-quality science, and his excitement with each new result, definitely shaped my understanding of what it means to be a good scientist.” 

Now Xian will be paying it forward with her own lab at VBRI and is excited to dive into the work. “Looking back to that kid in China and seeing how much I’ve grown, that’s what makes me most proud and motivates me to build a team where others can grow, too.” 

 
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