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J Peguet-Navarro

Publications and source records attributed to J Peguet-Navarro.

7 recordsLinked to original sources
PubMed2005

TGFbeta inhibits CD1d expression on dendritic cells.

The CD1 family of cell surface glycoprotein has been demonstrated to be a third lineage of antigen-presenting molecules for specific T cell responses. They present lipidic, glycolipidic antigen and hydrophobic peptide to T cells. CD1d restricted T cells play a role in autoimmune disease and in tumor immunity. Transforming growth factor beta (TGFbeta), a member of the family of polypeptide growth factors synthetized by human keratinocytes, has inhibitory effects on proliferation and differentiation of immune cells, especially on CD1d-restricted natural killer T cells. These properties led us to investigate the role of TGFbeta in CD1d expression on dendritic cells (DC), which are known to play a key role in initiation of the immune response. Here, we observed CD1d molecules on DC developed from PBMC with GM-CSF and IL4 but not with GM-CSF, IL4 and TGFbeta for 7 d. RT-PCR and FACS analysis (mAb 42.1) performed at various stages of differentiation on CD34+ HPC show that CD1d mRNA levels and CD1d molecule expression at the cell surface decreased progressively during the differentiation process. Thus, while committing DC-precursors differentiation toward the Langerhans cell (LC) pathway, TGFbeta likely inhibits CD1d transcription. Therefore, LC freshly recovered from epidermal sheet were evaluated by flow cytometry. In accordance with in vitro observation, they did not expressed measurable levels of CD1d molecules at the cell membrane. Thus, TGFbeta produced by keratinocytes contribute to selectively downregulate CD1d expression on intraepidermal-resident LC.

Antigens, CD1↗
PubMed2004

Determination of sunscreen immune protection factors using human dendritic cell suspensions.

In a previous study, we have used UVB-irradiated human skin explants and the allostimulatory function of Langerhans cells (LC) to determine immune protection factors (IPF) for sunscreens. We sought here to simplify the model by using either human enriched LC suspensions or in vitro generated dendritic cells from human monocytes (MoDC). LC or MoDC suspensions were irradiated with increasing doses of UVB through a piece of translucent strip recovered or not with the sunscreens. The allostimulatory function of the cells was then analysed in a mixed lymphocyte reaction and the UVB dose providing 50% immunosuppression (D50%) was determined graphically. IPF were determined by the ratio of the D50% value in the presence of sunscreen to that of the vehicle alone. In either experimental conditions, the D50% in the presence of sunscreens was significantly higher (p < 0.01) than that obtained with the vehicle, demonstrating the sunscreen immunoprotective effect. IPF values obtained with either DC suspensions were very similar and quite comparable to those previously obtained in the skin explant model. Thus, the present in vitro model provides easy tools to determine a new important biological parameter for sunscreens, i.e. immune protection.

Cell Separation↗
PubMed2001

Functional HIV CXCR4 coreceptor on human epithelial Langerhans cells and infection by HIV strain X4.

HIV can cross the intact epithelium of genital mucosae via Langerhans cells. Fresh Langerhans cells are known to express CD4 and CCR5. The presence of CXCR4 on the surface of cultured but not freshly isolated Langerhans cells has been described. In the present study, we demonstrate that CXCR4 was expressed by fresh Langerhans cells isolated and purified from epidermis. However, the percentage of Langerhans cells expressing CXCR4 or CCR5 increased during maturation of the cells in culture, especially in the presence of exogenous granulocyte-macrophage colony-stimulating factor. To determine whether CXCR4 was functional, freshly isolated Langerhans cells were infected with HIV LAI, a T-cell-tropic strain, and p24 protein production was measured in culture supernatants. p24 production was observed when infected Langerhans cells were cocultured with SupT1 cells. However, the presence of HIV provirus DNA was evidenced within the infected Langerhans cells by nested PCR. Ultrastructural studies confirmed the formation of syncytia when Langerhans cells were cocultured with SupT1 cells. Preincubation of Langerhans cells with azidothymidine or SDF-1-alpha, a natural ligand for CXCR4, prevented infection. These data demonstrated that CXCR4 is present on the surface of Langerhans cells freshly isolated from human skin epidermis and that this expression is functional.

CD4 Antigens↗
PubMed1996

Expression of gastrin-releasing peptide receptor in human skin.

Bombesin-related peptides are expressed in the skin of batrachians and mammals. As gastrin-releasing peptide belongs to this family, we searched for the presence and distribution of gastrin-releasing peptide receptors (GRPr) in the skin of healthy human adults by immunohistochemistry, flow cytometry and electron microscopy. The results indicated that GRPr are expressed on nerves and vessels in the dermis, on eccrine sweat glands, sebaceous glands and erector pili muscle. Within epidermis, staining was localized only on basal and suprabasal layer cells, or in the whole epidermis, according to the samples studied. Interestingly, suprabasal epidermal dendritic cells occasionally showed a strong labelling. Some of these epidermal dendritic cells were identified as Langerhans' cells by immunoelectron microscopy studies. Flow cytometry analysis of crude epidermal cell suspensions resulted in the expression of GRPr on about 43% of the cells. Therefore, we investigated whether human GRPr could modulate Langerhans' cells antigen-presenting functions. For this purpose, we added increasing concentrations of GRP (10(-12) to 10(-5) M) to mixed epidermal cell lymphocyte reactions. Allogeneic T-cell proliferation was not significantly modified when added to GRP-pretreated epidermal cells. In conclusion, we demonstrated the presence of GRPr in human skin, suggesting that GRP may modulate epidermal cell functions but does not modify antigenic presentation.

Adult↗
PubMed1996

In vitro primary sensitization of hapten-specific T cells by cultured human epidermal Langerhans cells--a screening predictive assay for contact sensitizers.

BACKGROUND: The need to develop predictive tests which could identify potential allergens has been recognized for many years. There is as yet no accepted in vitro method for the assessment of contact sensitizers. OBJECTIVE: We have tested the ability of a range of contact allergens to induce in vitro primary sensitization of autologous T cells. METHOD: T-cell proliferation induced by haptens using 2-day cultured human Langerhans cells as antigen-presenting cell was assessed by 3H thymidine incorporation. Antigen specific stimulation was calculated as stimulation indexes. RESULTS: Strong allergens induced in vitro a primary T-cell response in all (trinitrophenyl, TNP: 13/13) or in the majority (fluorescein isothiocyanate, FITC: 7/10) of experiments. An irritant, sodium dodecyl sulfate (SDS), failed to generate a significant T-cell proliferation in any of the experiments (0/10). We obtained a significant lymphoproliferative response to weak sensitizers only in a limited number of experiments: (coumarin: 1/12, citronellal: 0/10, hydroxycitronellal: 2/8). p-Phenylenediamine (PPDA), a prohapten and highly sensitizing chemical in vivo, generated primary sensitization in vitro in only one of six experiments, while Bandrowski's base (BB), a metabolization product of PPDA induced a significant T-cell response in all six experiments. CONCLUSION: The present in vitro model allows discrimination between two groups of substances: strong contact sensitizers (TNP, FITC, BB) on the one hand and weak sensitizers (coumarin, citronellal and hydroxycitronellal) and irritants (SDS) on the other hand. It could be used as a screening in vitro assay to eliminate strong contact allergens before further predictive animal tests have to be performed.

Coumarins↗