Showing papers by "Christophe Caux published in 1999"

The monoclonal antibody DCGM4 recognizes Langerin, a protein specific of Langerhans cells, and is rapidly internalized from the cell surface.

Abstract: We generated monoclonal antibody (mAb) DCGM4 by immunization with human dendritic cells (DC) from CD34+ progenitors cultured with granulocyte-macrophage colony-stimulating factor and TNF-alpha. mAb DCGM4 was selected for its reactivity with a cell surface epitope present only on a subset of DC. Reactivity was strongly enhanced by the Langerhans cell (LC) differentiation factor TGF-beta and down-regulated by CD40 ligation. mAb DCGM4 selectively stained LC, hence we propose that the antigen be termed Langerin. mAb DCGM4 also stained intracytoplasmically, but neither colocalized with MHC class II nor with lysosomal LAMP-1 markers. Notably, mAb DCGM4 was rapidly internalized at 37 degrees C, but did not gain access to MHC class II compartments. Finally, Langerin was immunoprecipitated as a 40-kDa protein with a pI of 5.2 - 5.5. mAb DCGM4 will be useful to further characterize Langerin, an LC-restricted molecule involved in routing of cell surface material in immature DC.

Regulation of dendritic cell trafficking: a process that involves the participation of selective chemokines

Abstract: DC function as sentinels of the immune system. They traffic from the blood to the tissues where, while immature, they capture antigens. They then leave the tissues and move to the draining lymphoid organs where, converted into mature DC, they prime naive T cells. This suggestive link between DC traffic pattern and functions led to the investigation of the chemokine responsiveness of DC during their development and maturation. These studies have shown that immature and mature DC are not recruited by the same chemokines. Immature DC respond to many CC- and CXC-chemokines (MIP-1alpha, MIP-1beta, MIP-5, MCP-3, MCP-4, RANTES, TECK, and SDF-1) and in particular to MIP-3alpha/LARC, which acts through CCR6, a receptor mainly expressed in DC and lymphocytes. Like most other chemokines acting on immature DC, MIP-3alpha is inducible on inflammatory stimuli. In contrast, mature DC have lost their responsiveness to most of these chemokines through receptor down-regulation or desensitization, but acquired responsiveness to MIP-3beta/ELC and 6Ckine/SLC as a consequence of CCR7 up-regulation. MIP-3alpha mRNA is only detected within inflamed epithelial crypts of tonsils, the site of antigen entry known to be infiltrated by immature DC, whereas MIP-3alpha and 6Ckine are specifically expressed in the T cell-rich areas where mature IDC home. These observations suggest a role for chemokines induced on inflammation such as MIP-3alpha in recruitment of immature DC at the site of injury and a role for MIP-3beta/6Ckine in accumulation of antigen-loaded mature DC in T cell-rich areas of the draining lymph node. A better understanding of the regulation of DC trafficking might offer new opportunities of therapeutic interventions to suppress or stimulate the immune response.

Respective involvement of TGF-beta and IL-4 in the development of Langerhans cells and non-Langerhans dendritic cells from CD34+ progenitors.

Abstract: In vivo, dendritic cells (DC) form a network comprising different populations. In particular, Langerhans cells (LC) appear as a unique population of cells dependent on transforming growth factor beta(TGF-beta) for its development. In this study, we show that endogenous TGF-beta is required for the development of both LC and non-LC DC from CD34+ hematopoietic progenitor cells (HPC) through induction of DC progenitor proliferation and of CD1a+ and CD14+ DC precursor differentiation. We further demonstrate that addition of exogenous TGF-beta polarized the differentiation of CD34+ HPC toward LC through induction of differentiation of CD14+ DC precursors into E-cadherin+, Lag+CD68-, and Factor XIIIa-LC, displaying typical Birbeck granules. LC generated from CD34+ HPC in the presence of exogenous TGF-beta displayed overlapping functions with CD1a+ precursor-derived DC. In particular, unlike CD14(+)-derived DC obtained in the absence of TGF-beta, they neither secreted interleukin-10 (IL-10) on CD40 triggering nor stimulated the differentiation of CD40-activated naive B cells. Finally, IL-4, when combined with granulocyte-macrophage colony-stimulating factor (GM-CSF), induced TGF-beta-independent development of non-LC DC from CD34+ HPC. Similarly, the development of DC from monocytes with GM-CSF and IL-4 was TGF-beta independent. Collectively these results show that TGF-beta polarized CD34+ HPC differentiation toward LC, whereas IL-4 induced non-LC DC development independently of TGF-beta.

Dendritic cells directly modulate B cell growth and differentiation.

Abstract: A cardinal feature of Langerhans cells or dendritic cells (DC) located within the mucosal epithelium is to capture foreign antigens after tissue injury and subsequently initiate immune responses. While migrating through the draining afferent lymph into the proximal secondary lymphoid organ, DC process the antigens. Within paracortical areas of the secondary lymphoid organs, DC [referred to in this localization as interdigitating dendritic cells (IDC)] select the rare antigen-specific T and B cells [1, 2]. IDC have the unique capacity to stimulate antigen-specific naive T cells to proliferate, secrete cytokines, and express CD40L [3–5]. In murine models, immunohistological studies have demonstrated that primary T cell-dependent B cell responses were initiated within the T cell/IDC-rich areas [6]. Activated T cells stimulate antigen-specific naive B cells to proliferate and to differentiate into germinal center founder cells or into short-lived plasma cells producing essentially immunoglobulin M (IgM) [7]. The germinal center reaction starts with the colonization of primary follicles by germinal center founder cells. Antigen transporting cells have been identified that trap immune complexes in the lymph and move these complexes onto the follicular dendritic cell network within the follicles [8]. The nature of such antigen transporting cells has not yet been formally identified. Within the follicles, follicular dendritic cells, which are probably not of hemopoietic origin, retain immune complexes, thus allowing B cells to endocytose, process, and present the antigen to CD4 T cells. After intense proliferation of centroblasts in the dark zone, irreversible events occur during the germinal center reaction that lead to isotype-switched B cells with high affinity for the antigen that eventually differentiate into either memory B cells or plasma cells. Apart from the critical role of DC in the initiation of cellular immune responses [4], several experiments strongly support their direct involvement in the regulation of humoral responses. Our studies now provide evidence that human DC directly interact with B cells in vitro and regulate mature B cell responses at various stages of their differentiation.

Toward a Role of Dendritic Cells in the Germinal Center Reaction: Triggering of B Cell Proliferation and Isotype Switching

Abstract: We have reported previously that in vitro generated dendritic cells (DC) can directly regulate B cell responses. Recently, germinal center DC (GCDC) were identified within B cell follicles. Due to their particular localization, we have tested in the present study whether GCDC could contribute to key events characteristic of the GC reaction. Our present results demonstrate that 1) ex vivo GCDC induce a dramatic GC B cell expansion upon CD40 and IL-2 activation and drive plasma cell differentiation, 2) this property is shared by GCDC and blood DC, but not by Langerhans cells, 3) IL-12 production by GCDC is critical in GC B cell expansion and differentiation, and 4) importantly, GCDC also induce IL-10-independent isotype switching toward IgG1. These observations support the novel concept that GCDC directly contribute to the germinal center reaction.