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From the * Division of Immunology, Allergy and Infectious Diseases, Department of Dermatology, We have recently described a system for the generation of dendritic cells (DC) and Langerhans
cells (LC) from defined CD34+ precursors purified from peripheral blood of healthy adult volunteers (). This study has now been extended by the characterization of two distinct subpopulations of CD34+ cells in normal human peripheral blood as defined by the expression of the
skin homing receptor cutaneous lymphocyte-associated antigen (CLA). CD34+/CLA+ cells
from normal peripheral blood were found to be CD71LOW/CD11a+/CD11b+/CD49d+/
CD45RA+ whereas CD34+/CLA
Institute of Transfusion Medicine, University of Vienna Medical School, A-1090 Vienna, Austria;
and § Contrat jeune formation Institut National de la Santé et de la Recherche Médicale,
94-03, Etablissement de Transfusion Sanguine, F-67065 Strasbourg, France
cells displayed the CD71+/CD11aLOW/CD11bLOW/CD49d(+)/
CD45RALOW phenotype. To determine the differentiation pathways of these two cell populations, CD34+ cells were sorted into CLA+ and CLA
fractions, stimulated with GM-CSF and
TNF-
in vitro, and then were cultured for 10 to 18 d. Similar to unfractionated CD34+ cells,
the progeny of both cell populations contained sizable numbers (12-22%) of dendritically
shaped, CD1a+/HLA-DR+++ cells. In addition to differences in their motility, the two dendritic cell populations generated differed from each other by the expression of LC-specific
structures. Only the precursors expressing the skin homing receptor were found to differentiate into LC as evidenced by the presence of Birbeck granules. In contrast, CLA
precursor cells
generated a CD1a+ DC population devoid of Birbeck granule-containing LC. Provided that
comparable mechanisms as found in this study are also operative in vivo, we postulate that the
topographic organization of the DC system is already determined, at least in part, at the progenitor level.
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