JOURNAL OF INTERFERON AND CYTOKINE RESEARCH 19:471±478 (1999) Mary Ann Liebert, Inc. IFN-b Interferes with the Differentiation of Dendritic Cells from Peripheral Blood Mononuclear Cells: Selective Inhibition of CD40-Dependent Interleukin-12 Secretion EMMANUEL J. BARTHOLOMÉ , 1 FABIENNE WILLEMS, 1,2 ALAIN CRUSIAUX, 1 KRIS THIELEMANS, 3 LILIANE SCHANDENE, 1 and MICHEL GOLDMAN 2 ABSTRACT We studied the effects of interferon-b (IFN- b ) on the differentiation of dendritic cells (DC) obtained by cul- turing plastic-adherent peripheral blood mononuclear cells (PBMC) from a total of 30 healthy volunteers in the presence of granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-4 (IL-4). First, we found that the addition of IFN- b at the initiation of the culture did not modify DC morphology but caused a reproducible and statistically significant upregulation of HLA-DR, CD86, and CD80 surface expression. CD1a expression was significantly reduced, and CD40 expression was unchanged. We then determined the influence of IFN- b on the production of cytokines by DC. DC differentiated in the presence of IFN- b secreted significantly less IL-12 (p40 and p70) both spontaneously and on activation by fibroblasts transfected with the CD40L gene. This effect of IFN-b was dose dependent and selective, as it was not observed for IL-6, IL- 8, and tumor necrosis factor- a (TNF- a ). As a consequence, DC differentiated in the presence of IFN- b in- duced significantly less IFN- c secretion by alloreactive T cells, whereas they were more efficient than control DC in eliciting IL-5 secretion. We conclude that the direct action of IFN- b on DC causes inhibition of their ability to secrete IL-12 in response to CD40 ligation and to elicit Th1 type responses. 471 INTRODUCTION T HE PIVOTAL ROLE OF DENDRITIC CELLS (DC) in the induction of immune responses is now well established (reviewed in ref. 1). Located in most tissues, immature DC actively capture and process antigens. In response to microbial products or in- flammatory cytokines or both, DC mature and migrate to lym- phoid organs, where they activate antigen-specific T cells. The process of maturation is a crucial step in the development of DC into fully potent antigen-presenting cells (APC) able to in- duce optimal activation of naive T cells. During maturation, DC lose their ability to capture and process antigens, increase their expression of MHC class II and costimulatory molecules, and upregulate their production of cytokines, such as interleukin (IL)-12. Initiated in nonlymphoid tissues by a variety of fac- tors, DC maturation is achieved after CD40 engagement by CD40 ligand (CD40L)-expressing T cells. (2±8) Several pathways of DC differentiation exist, and human DC of myeloid origin can be generated in vitro with appropriate cy- tokines either directly from bone marrow-derived CD34 pro- genitors or from peripheral blood monocytes (reviewed in ref. 9). It is obviously important to identify the factors that might affect the differentiation of DC from their precursors. During inflammatory processes, several cytokines are produced that might influence the differentiation and maturation of DC. In- deed, IL-7 and IL-13 were shown to be able to substitute for IL-4 for generation of DC from human blood monocytes. (10±12) On the contrary, IL-10 and interferon (IFN)- g prevent the gen- eration of DC induced by granulocyte-macrophage colony- stimulating factor (GM-CSF) and IL-4 and favor the develop- ment of macrophages. (13,14) Moreover, transforming growth factor- b1 (TGF-b1), in the presence of GM-CSF and IL-4, pro- motes the differentiation of monocytes into Langerhans cells, a particular subclass of DC present in the epidermis, bronchi, and mucosae. (15) Type I IFN are produced by different cell types in response to viral, bacterial, and protozoan infections but also in response to inflammatory cytokines, such as IL-1 or tumor necrosis fac- 1 Department of Immunology, Hôpital Erasme, and 2 Centre de Recherche Inter-Universitaire en Vaccinologie (C.R.I.V.), Universit… Libre de Bruxelles, Brussels, Belgium. 3 Laboratory of Physiology-Immunology, Vrije Universiteit Brussel, Brussels, Belgium.