DELINEATION OF THE DENDRITIC CELL LINEAGE BY GENERATING LARGE NUMBERSOF BIRBECK GRANULE-POSITIVE LANGERHANS CELLS FROM HUMAN PERIPHERAL-BLOOD PROGENITOR CELLS IN-VITRO

It is well established by in vivo and in vitro studies that dendritic cells (DCs) originate from hematopoietic progenitor cells. However, th e presumed intermediate of Birbeck granule (BG)(+) Langerhans cells (L Cs) has not been detected in cultures derived from bone marrow or peri pheral blood progenitor cells (PBPCs), thus contrasting with the data obtained with cord blood. We show here that large numbers of BG(+) LCs can be generated from human CD34(+) PBPCs in vitro, when granulocyte- macrophage colony-stimulating factor and interleukin-4, potent promote rs of LC/DC differentiation, are combined with a cocktail of early act ing hematopoietic growth factors. LCs were found to emerge from CD33()CD11b(+)CD14(-) progenitor cells that they share with the monocytic l ineage. During culture, these cells exhibited a sequence of dramatic m orphologic changes, starting with a major increase in granularity foll owed by an increase in size herein exeeding that of all peripheral blo od cells. At the same time, CD1a and major histocompatibility complex class II expression were upregulated and virtually all CD1a(++) cells were BG(+) by electron microscopy. With prolonged culture, CD1a was do wnregulated on a major population of cells, paralleled by a loss of BG and an increase of CD4, CD25, and CD80 expression that may correspond to the maturation of epidermal LC in vitro. However, these cells were consistently CD5(-) and did not exhibit changes in the CD45-isoform e xpression during culture. The availability of large numbers of these h ighly purified BG(+) LCs and mature DCs allows for specific analysis o f these subpopulations and provides a source of potent antigen-present ing cells from individual patients for Vaccination protocols against i nfectious or tumor-associated antigens. (C) 1995 by The American Socie ty of Hematology.