Journal of Nuclear Medicine 2010-04-15
Nanobodies as Tools for In Vivo Imaging of Specific Immune Cell Types.
Kurt De Groeve, Nick Deschacht, Celine De Koninck, Vicky Caveliers, Tony Lahoutte, Nick Devoogdt, Serge Muyldermans, Patrick De Baetselier, Geert Raes
PMID 20395332
Abstract
Nanobodies are single-domain antigen-binding fragments derived from heavy-chain antibodies that are devoid of light chains and occur naturally in Camelidae. We have shown before that their small size and high affinity and specificity for their target antigen make Nanobodies ideal probes for in vivo tumor imaging. In the present study, we have evaluated the use of Nanobodies as a generic method for imaging the in vivo biodistribution of specific immune cell types, using myeloid cells as an example. METHODS: The cellular specificity of Nanobodies raised against murine bone marrow-derived dendritic cells was verified using flow cytometry on a range of myeloid and nonmyeloid cell types. The Nanobodies were then labeled with (99m)Tc and their biodistribution was analyzed using SPECT. The biodistribution was also assessed by measuring radioactivity in various organs and tissues. To verify whether the observed biodistribution was due to specific targeting through the antigen-binding loops, rather than retention in organs because of effects of the framework regions, we genetically grafted the antigen-binding loops of the Nanobodies onto the framework region of a Nanobody scaffold that by itself showed low background retention in the periphery
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