Human melanoma cells inhibit the earliest differentiation steps of human Langerhans cell precursors but failed to affect the functional maturation of epidermal Langerhans cells

Tumour-derived factors suppress differentiation and function of in vitro generated DC. Here, we investigate the effect of two melanoma clones differing in their invasive and metastatic properties on the generation and/or functional maturation of human epidermal LC. LC were generated from CD34+ cord blood progenitors under GM-CSF/TNF-α/TGF-β1. CD34+ cells were co-cultured with or without melanoma cells using Transwell dishes. After 11 days of co-culture, CD34+-derived cells display a non-adherent undifferentiated morphology, a high level of monocytic CD14 marker, a down-regulated expression of LC markers (CD1a, E-cadherin) and DC markers (CD40, CD80, CD54, CD58, CD83, CD86, HLA-DR, HLA-class I). These cells were less potent than control LC in inducing allogeneic T cell proliferation. The generation of the CD14+ population was correlated with a decrease in the CD1a+ population, without any statistical differences between the two clones. Melanoma cells diverted the differentiation of CD34+ cells towards a dominant CD14+ population only if the progenitors were in an early growth phase. IL-10, TGF-β1 and VEGF were not responsible for these effects, as assessed by using blocking antibodies. By contrast, co-culture of fresh epidermal LC with melanoma cells did not affect their phenotype and function. Our data demonstrate that melanoma cells inhibit the earliest steps of LC differentiation, but failed to affect the functional maturation of epidermal LC. This suggests that melanoma cells participate in their own escape from immunosurveillance by preventing LC generation in the local cutaneous microenvironment. © 2001 Cancer Research Campaign http://www.bjcancer.co

Immature and Maturation-Resistant Human Dendritic Cells Generated from Bone Marrow Require Two Stimulations to Induce T Cell Anergy In Vitro

Immature dendritic cells (DC) represent potential clinical tools for tolerogenic cellular immunotherapy in both transplantation and autoimmunity. A major drawback in vivo is their potential to mature during infections or inflammation, which would convert their tolerogenicity into immunogenicity. The generation of immature DC from human bone marrow (BM) by low doses of GM-CSF (lowGM) in the absence of IL-4 under GMP conditions create DC resistant to maturation, detected by surface marker expression and primary stimulation by allogeneic T cells. This resistence could not be observed for BM-derived DC generated with high doses of GM-CSF plus IL-4 (highGM/4), although both DC types induced primary allogeneic T cell anergy in vitro. The estabishment of the anergic state requires two subsequent stimulations by immature DC. Anergy induction was more profound with lowGM-DC due to their maturation resistance. Together, we show the generation of immature, maturation-resistant lowGM-DC for potential clinical use in transplant rejection and propose a two-step-model of T cell anergy induction by immature DC

Les tétraspanines dans la physiopathologie de la peau

Les tétraspanines sont des protéines transmembranaires qui interagissent entre elles et avec d’autres protéines telles que des intégrines, des protéines à domaines immunoglobulines, des récepteurs à facteurs de croissance et à cytokines. Elles participent ainsi à l’organisation de réseaux de signalisation à la membrane plasmique des cellules. Bien qu’elles soient exprimées abondamment et souvent de façon ubiquitaire, leur fonction a été peu étudiée à ce jour. Il est toutefois bien établi qu’elles régulent l’adhésion cellulaire, la migration, l’invasion, la survie ou l’infection par les virus. Les mécanismes moléculaires sous-jacents restent cependant à élucider. Nous exposerons dans cette revue quelles sont les différentes tétraspanines exprimées par les cellules de l’épiderme et quels rôles elles jouent dans la physiopathologie cutanée, et en particulier dans la cancérogenèse

Unusual lactam formation occurring in the synthesis of a biotinylated T-antigen-serine derivative.

International audienceSynthesis of the biotinylated T-antigens, linked to a serine by an alpha (7 alpha) or a beta (7 beta) 2-acetamido-2-deoxy-D-galactoside bond, is described. These derivatives were needed for the detection of a specific endogenous lectin at the surface and/or on the migration pathway of melanoma cells. In the course of the synthesis, an unusual lactam formation was observed with the beta anomer of the azido-disaccharide 5 beta

Induction of IgG antibodies directed to a M(r) 31,000 melanoma antigen in patients immunized with vaccinia virus melanoma oncolysates.

Pre- and postimmunization sera from eight tumor-free melanoma patients undergoing vaccinia melanoma oncolysate (VMO) therapy were used to investigate the humoral response to antigens from infected and uninfected melanoma cells and from vaccinia virus. Immunodetection on Western blots showed that all patients, in addition to reacting to several other proteins, developed IgG antibodies to a M(r) 31,000 protein antigen within 1 month of immunization. This M(r) 31,000 antigen is expressed both on VMO and on melanoma metastases in situ, disappears in primary cultures of these metastases, and is absent in extracts from vaccinia virus, from human melanoma cell lines, and from normal melanocytes, suggesting that this M(r) 31,000 protein is reexpressed following vaccinia virus infection of human melanoma cells. Periodate treatment of the blotted antigens abolished reactivity of patients' postimmunization sera with the M(r) 31,000 antigen, thus showing that this antigen is a glycoprotein and that the relevant epitope is likely to reside on its carbohydrate moiety. These anti-M(r) 31,000 IgG antibodies were absent in the sera of VMO-treated patients before immunization, absent in the serum of a normal donor hyperimmunized with vaccinia virus, and absent in normal human sera. In addition, these anti-M(r) 31,000 antibodies appeared 1 week after the first VMO injection, remained stable during the treatment, and decreased when the treatment was stopped. Such antibodies can also be demonstrated in sera of melanoma patients bearing metastases but disappeared following resection of their metastases. Thus, in melanoma patients, immunization with VMO induces an antibody response directed against a M(r) 31,000 glycoprotein likely to represent a new melanoma antigen. Further identification of this antigen could be of utmost interest for the further development of melanoma vaccines

Poly(I:C)-Treated human langerhans cells promote the differentiation of CD4+ T cells producing IFN-gamma and IL-10.

International audienceEpidermal Langerhans cells (LCs) are the first dendritic cells to encounter skin pathogens. However, their function has recently been challenged, especially in the initiation of T-cell responses to viral antigens. We have previously reported that fresh immature human LCs express mRNA encoding TLR3. Here we analyze the response of highly purified human LCs to poly(I:C), a synthetic mimetic of viral dsRNA recognized by TLR3. We show that LCs exposed for 2 days to poly(I:C) under serum-free conditions up-regulated co-stimulatory molecules, a process associated with increased allostimulatory capacity. Furthermore, poly(I:C) significantly enhanced LC survival and induced them to produce CXCL10, IL-6, and IL-12 p40. Bioactive IL-12 p70, IL-1beta, IL-15, IL-18, and IL-23 were never detected, even after CD40 ligation. LC incubation in the presence of bafilomycin completely reversed the effect of poly(I:C) on LC phenotypic activation and survival, indicating that endosomal TLR3 is involved in this process. Most interestingly, we report here that poly(I:C)-treated LCs favored alloreactive CD4(+) T-cell differentiation toward a Th1 profile and concomitant differentiation of IL-10-producing CD4(+) T cells that might limit, at another time, the inflammatory response and subsequent tissue damage