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Updated: Jun 16, 2026
Non-invasive Imaging of Leukocyte Homing and Migration in vivo
Published on: December 5, 2010
Imaging leukocyte trafficking in vivo with two-photon-excited endogenous tryptophan fluorescence
Chunqiang Li1, Riikka K Pastila, Costas Pitsillides
1Wellman Center for Photomedicine and Center for Systems Biology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA. Li.Chunqiang@mgh.harvard.edu
Insights
This study introduces an innovative in vivo imaging technique for leukocytes using natural protein fluorescence. This method allows real-time observation of leukocyte dynamics in skin without exogenous labels, aiding inflammation research.
Area of Science:
- Biomedical Optics
- Cellular Biology
- Immunology
Background:
- Leukocyte trafficking is crucial in inflammatory responses.
- Current imaging methods often require exogenous labels, limiting in vivo applications.
- Understanding leukocyte behavior in real-time is essential for disease monitoring.
Purpose of the Study:
- To develop a novel, label-free method for in vivo leukocyte imaging.
- To visualize dynamic leukocyte-endothelial interactions in inflamed skin.
- To track leukocyte extravasation and migration in dermal tissue.
Main Methods:
- Utilizing two-photon excitation of endogenous tryptophan fluorescence in the UV spectral region.
- Employing near 590 nm excitation for noninvasive optical sectioning of mouse skin.
- Applying video-rate and time-lapse microscopy for dynamic observation.
Main Results:
- Successfully imaged leukocytes in vivo by exciting endogenous protein fluorescence.
- Observed dynamic interactions between leukocytes and dermal vascular endothelium.
- Demonstrated significant enhancement of leukocyte rolling, adhesion, and infiltration during inflammation.
- Distinguished motile leukocytes from non-motile resident autofluorescent cells.
Conclusions:
- The developed method provides label-free, real-time imaging of leukocytes in vivo.
- This technique facilitates the study of leukocyte dynamics during inflammation.
- Potential applications include monitoring inflammatory processes and tracking leukocytes in humans.
Abstract:
We describe a new method for imaging leukocytes in vivo by exciting the endogenous protein fluorescence in the ultraviolet (UV) spectral region where tryptophan is the major fluorophore. Two-photon excitation near 590 nm allows noninvasive optical sectioning through the epidermal cell layers into the dermis of mouse skin, where leukocytes can be observed by video-rate microscopy to interact dynamically with the dermal vascular endothelium. Inflammation significantly enhances leukocyte rolling, adhesion, and tissue infiltration. After exiting the vasculature, leukocytes continue to move actively in tissue as observed by time-lapse microscopy, and are distinguishable from resident autofluorescent cells that are not motile. Because the new method alleviates the need to introduce exogenous labels, it is potentially applicable for tracking leukocytes and monitoring inflammatory cellular reactions in humans.
