Leon Grayfer, PhD
Associate Professor
Department of Biological Sciences
George Washington University
Email: [email protected]
I have been fascinated by how immune systems interact with and shape the physiology of vertebrate organisms since my undergraduate days at the University of Alberta, Canada. During my undergraduate research and graduate studies, I investigated how bony fish regulate antimicrobial immune responses, with a particular focus on macrophages, highly versatile cells that not only coordinate host defense but also contribute to development, tissue homeostasis, repair, and regeneration. This broader interest in macrophage biology and the interactions between immunity and tissue physiology led me to a postdoctoral fellowship at the University of Rochester, where I began using the amphibian Xenopus laevis to investigate immune cell development and function.
Today, as an Associate Professor of Biological Sciences at George Washington University, I lead a research program exploring how immunity, development, and tissue physiology intersect. My group uses Xenopus laevis and other comparative approaches to investigate how immune cells develop and become functionally specialized, how they communicate with tissues during homeostasis and injury, and how these interactions influence host defense, wound repair, and regeneration. We are particularly interested in understanding how these processes have evolved across vertebrates and how they contribute to differences in susceptibility, resistance, and recovery from disease.
Associate Professor
Department of Biological Sciences
George Washington University
Email: [email protected]
I have been fascinated by how immune systems interact with and shape the physiology of vertebrate organisms since my undergraduate days at the University of Alberta, Canada. During my undergraduate research and graduate studies, I investigated how bony fish regulate antimicrobial immune responses, with a particular focus on macrophages, highly versatile cells that not only coordinate host defense but also contribute to development, tissue homeostasis, repair, and regeneration. This broader interest in macrophage biology and the interactions between immunity and tissue physiology led me to a postdoctoral fellowship at the University of Rochester, where I began using the amphibian Xenopus laevis to investigate immune cell development and function.
Today, as an Associate Professor of Biological Sciences at George Washington University, I lead a research program exploring how immunity, development, and tissue physiology intersect. My group uses Xenopus laevis and other comparative approaches to investigate how immune cells develop and become functionally specialized, how they communicate with tissues during homeostasis and injury, and how these interactions influence host defense, wound repair, and regeneration. We are particularly interested in understanding how these processes have evolved across vertebrates and how they contribute to differences in susceptibility, resistance, and recovery from disease.
Elissa Chapkin
Research Associate
Ellie contributes to research across the Grayfer Lab, working at the intersection of immunology, developmental biology, tissue physiology, wound repair, regeneration, and host–microbe interactions. Her work spans multiple experimental systems and projects, with responsibilities including experimental planning and execution, amphibian tissue and immune cell isolation, cellular and molecular assays, microscopy, flow cytometry, molecular biology, infection studies, and preparation and analysis of samples for genomic and transcriptomic approaches.
Ellie works closely with students, and collaborators to develop and carry out experiments, troubleshoot protocols, analyze and interpret data, and contribute to ongoing research projects. She is involved in investigations of immune cell development and function, immune–tissue interactions, responses to infection, and the cellular mechanisms underlying tissue repair and regeneration. Through her involvement across diverse projects, Ellie plays an important role in connecting experimental approaches and research questions throughout the laboratory.
Graduate Students
Ryley Crow
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Undergraduate Students
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Anastasia Clark
Ana’s research investigates how the frog skin immune system interacts with the microbiome to maintain tissue health and protect against infection. Her work examines how immune cells and resident microbes communicate within the skin, and how these interactions influence immune responses, microbial community composition, and tissue function. By studying the dynamic relationship between host immunity and the skin microbiome, her research seeks to understand how amphibians balance protection from pathogens with tolerance of their microbial environment. Lilliana Sosa Lilli’s research examines how mast cells regulate skin physiology and contribute to protection against fungal infection in frogs. Her work investigates how these specialized immune cells sense and respond to changes at the skin surface, communicate with surrounding tissues, and shape local immune and physiological responses. By studying mast cell function during fungal infection, her research seeks to uncover how the skin integrates immune defense with tissue homeostasis and protection from pathogens. Lyn Kerry Lyn’s research investigates how antigen-presenting cells, including dendritic cells and macrophages, respond to skin injury and microbial challenge. He is particularly interested in how these cells detect antigens within damaged tissue, communicate with other immune cells, and shape the inflammatory response during wound repair. By studying these interactions in X. laevis, his work examines how antigen-presenting cells can support both effective defense against pathogens and the restoration of healthy skin. This work provides insight into how immune surveillance, inflammation, and tissue repair are coordinated at the skin interface. |
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Former Grayfer Lab Members
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Christina Griffith Garvey, PhD Chrissy’s doctoral research focused on wound repair and the role of macrophages in scarless tissue regeneration. Her work examined how macrophage responses and functions changed across different life stages and how these developmental differences influenced the outcome of wound healing. By studying macrophage behavior during regeneration, she investigated how immune cells contributed to the balance between inflammation, tissue repair, and scar formation, providing insight into the mechanisms that allowed tissues to heal with minimal scarring. Muhammad 'Riad' R. H. Hossainey, PhD Riad’s doctoral research examined how macrophage differentiation shapes their ability to control viral, mycobacterial, and fungal infections. His work defined how distinct macrophage differentiation states influence their functional responses to pathogens and, ultimately, determine infection outcomes. By linking macrophage differentiation to pathogen control, his research highlighted how immune cell identity and functional specialization can shape the course of infection. Riad is presently a postdoctoral fellow at the U.S. Food and Drug Administration (FDA), where he continues to build on his research experience in immunology. Kelsey Hauser, PhD Kelsey’s doctoral research focused on how distinct granulocyte lineages contributed to antiviral and antifungal immunity across amphibian development. Her work examined how immune cell functions changed during metamorphosis and how developmental stage influenced immune defenses at key mucosal barriers, including the skin and intestine. She also demonstrated that mast cells in frog skin played a critical role in protecting the host against the chytrid fungus Batrachochytrium dendrobatidis (Bd), highlighting the importance of tissue-resident immune cells in frontline pathogen defense. Kelsey is presently a postdoctoral researcher at Noblis, where she continues to apply her scientific expertise to biomedical and translational research. Amulya Yaparla, PhD Amulya’s doctoral research focused on understanding how amphibians regulated hematopoiesis and how specific growth factors control the development and functional specialization of different blood cell lineages. Her work demonstrated that Xenopus laevis myeloid precursors segregated to the bone marrow, distinguishing them from the peripheral liver, which serves as the primary site of blood cell development in this species. She also investigated how macrophage growth factors shape the development and functional capacities of these cells, including their ability to recognize and respond to pathogens. Together, her work provided new insight into the developmental regulation of amphibian immune cells and how the signals that control their differentiation ultimately influence immune function. Amulya is presently a Senior Scientist I in Bioprocess Development at Arcellx. Tyler Moore, MSc Tyler’s masters research investigated how developmental stage-dependent differences in macrophage biology shape antiviral immune responses. His work examined how macrophages change in their functional properties across development and how these changes influence their capacity to recognize, respond to, and control viral infections. By linking macrophage differentiation and maturation with antiviral function, his research highlighted how immune cell development can fundamentally influence infection outcomes. Tyler is now a Research Associate III at LGC Diagnostics & Genomics. Namarta Kalia, PhD Namarta’s postdoctoral research challenged the conventional view that developing amphibians are inherently more susceptible to viral infection. Using Xenopus laevis and Frog Virus 3 (FV3), she showed that tadpoles are unexpectedly more resistant to kidney infection than metamorphic and adult frogs. Her work revealed that this resistance is driven by endogenous retroviruses (ERVs), which stimulate antiviral interferon responses, and by specialized myeloid cells that populate the tadpole kidney. These findings uncovered a previously unrecognized developmental mechanism linking immune cell recruitment, ERV activity, and antiviral defense, demonstrating that greater immune maturity does not necessarily translate into greater resistance to infection. Namarta is now a Neurobiology Research Specialist at UCSD. Milan Popovic, PhD Milan’s postdoctoral research investigated how macrophage differentiation shapes susceptibility and resistance to mycobacterial infection. Using the Xenopus laevis–Mycobacterium marinum model, he showed that macrophages generated in response to CSF-1 are more susceptible to infection and support mycobacterial persistence and spread, whereas IL-34-derived macrophages are more resistant and more effective at eliminating intracellular bacteria. Importantly, these differences were also observed in human macrophages, highlighting how macrophage specialization can determine the outcome of mycobacterial disease and potentially inform more targeted approaches to tuberculosis. Milan is now a Senior Scientist at Beckman Coulter Life Sciences. |
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Past Undergraduate Students
Connor Barley Jonathan Ghaul Daphne Koubourli Emily Wendel Mira Zelle Omar Saadi Zarafsha Uzzaman America Lugo Julia Singer Netra Ranganathan Jasmina Gafurova Zoe Ilgenfritz Hamerenoah Tesega Daniel Messmer Sanjana Maddipudi |
Past High School Students
Aashish Batheja Hannah Docter-Loeb Mattie Melnyk Phillip Reeves Grace Chong Aishani Patnaik Niharika Chandra Chrestiane Tekola Ronith Pasula Nidhi Chinthakindi Iryne Jackson Maya Ensley |