GENERATION OF HUMAN DENDRITIC CELLS LANGERHANS CELLS FROM CIRCULATINGCD34(+) HEMATOPOIETIC PROGENITOR CELLS

Human Langerhans cells (LC) are CD1a(+) dendritic cells (DC) that func tion as potent antigen-presenting cells for primary and secondary immu ne responses. Limitations in DC/LC numbers, imposed by difficult and t edious isolation procedures, have so far precluded their use as immuno gens in the generation and/or augmentation of host responses against v arious pathogens. Therefore, we have developed a procedure for the gen eration of human DC/LC from CD34(+) hematopoietic progenitor cells (HP C) isolated (mean: 0.7 x 10(6)/buffy coat and 2.6 x 10(6)/leukapheresi s product) and purified (>95%) from the peripheral blood of healthy ad ults. In vitro stimulation of these cells with granulocyte-macrophage colony-stimulating factor (GM-CSF) and tumor necrosis factor (TNF)-alp ha led to their vigorous proliferation and differentiation resulting i n the emergence of CD45(+)/CD68(+)/CD3(-)/CD19(-)/CD56(-) leukocytes s ome of which (mean: 12%) express CD1a and exhibit anti-CD4 and anti-ma jor histocompatibility complex (MHC) class II reactivity. These CD1a() leukocytes include (1) LC as evidenced by the presence of Birbeck gr anules (BG), (2) CD14(+) monocytes, and (3) Birbeck granule-negative c ells with a dendritic morphology, Addition of interleukin (IL)-4 to th e cytokine cocktail interfered with the development of monocytes and l ed to a reduction in the overall cell yield but, on the other hand, re sulted in an increased percentage of CD1a(+) cells (mean: 24%) among a ll cells generated. In vitro generated CD1a(+), but not CD1a(-) HPC-de rived cells are potent stimulators of the primary mixed leukocyte reac tion and, as such, promising candidates for vaccination purposes. (C) 1996 by The American Society of Hematology.