International Immunology, Vol. 11, No. 1, 63-69,
January 1999
© 1999 Japanese Society for Immunology
Characterization of prethymic progenitors within the chicken embryo
Turku Immunology Centre, Department of Medical Microbiology, University of Turku, Kiinamyllynkatu 13, 20520 Turku, Finland
1 European Molecular Biology Laboratory, 69117 Heidelberg, Germany
2 Department of Oncology, Turku University Central Hospital, 20520 Turku, Finland
Correspondence to: J. Liippo
The thymic primordium in both birds and mammals is first colonized by cells emerging from the intra-embryonic mesenchyme but the nature of these precursors is poorly understood. We demonstrate here an early embryonic day 7 prethymic population with T lymphoid potential. Our work is a phenotypic analysis of, to date, the earliest embryonic prethymic progenitors arising in the avian para-aortic area during ontogeny. The phenotype of these cells, expressing the cell surface molecules 
2ß1 integrin, c-kit, thrombomucin/MEP21, HEMCAM and chL12, reflects functional properties required for cell adhesion, migration and growth factor responsiveness. Importantly, the presence of these antigens was found to correlate with the recolonization of the recipient thymus following intrathymic cell transfers. These intra-embryonic cells were also found to express the Ikaros transcription factor, the molecular function of which is considered to be prerequisite for embryonic lymphoid development.
Keywords: cell surface molecules, hematopoiesis, T lymphocytes, thymus, transcription factors
3 Present address: Biomedical Research Centre, Department of Medical Genetics, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
The first two authors contributed equally to this work