Dual role of dendritic cells in the induction and down-regulation of antigen-specific cutaneous inflammation.

We have previously reported that contact sensitivity (CS) to dinitrofluorobenzene (DNFB) in C57BL/6 mice was mediated by MHC class I-restricted CD8+ T cells and down-regulated by MHC class II-restricted CD4+ T cells. In this study, we analyzed the contribution of dendritic cells (DC) in the induction of these two T cell subsets endowed with opposite functions. Hapten-pulsed skin- and bone marrow-derived DC, obtained from either normal C57BL/6 mice or from MHC class II (I+ II-) and MHC class I (I- II+)-deficient mice, were tested for their ability to prime normal mice for CS to dinitrofluorobenzene. Expression of MHC class I molecules by transferred DC was mandatory both for the induction of CS and for the generation of hapten-specific CD8+ T cells in lymphoid organs. I+ II- DC were as potent as I+ II+ DC in priming for CS, demonstrating that activation of effector CD8+ T cells can occur independently of CD4+ T cell help. I- II+ DC could not immunize for CS, although they could sensitize for a delayed-type hypersensitivity reaction to protein Ags. Moreover, I- II+ DC injected simultaneously with cutaneous sensitization down-regulated the inflammatory response, suggesting that hapten presentation by MHC class II molecules could prime regulatory CD4+ T cells. These results indicate that DC can present haptenated peptides by both MHC class I and class II molecules and activate Ag-specific CD8+ effector and CD4+ regulatory T cell subsets, concurrently and independently.

[Physiopathology of eczema]. / Physiopathologie de l'eczéma.

Eczema is a skin inflammatory reaction mediated by antigen-specific T cells. Two main disorders belong to this group: contact dermatitis and atopic dermatitis. The pathophysiological mecanisms involved in both disorders are similar and include, at the cellular level, three elements: the antigen (hapten or environmental antigen), antigen-presenting cells belonging to the group of dendritic cells and antigen-specific T cells. The Langerhans cell responsible for antigen handling and presentation to specific T cells appears to play a central role for the generation of the inflammatory reaction.

[Disseminated cutaneous neurilemmomatosis]. / Neurilemmomatose cutanée disséminée.

INTRODUCTION: Neurilemmomatosis is a rare, non-inherited disease which has several features similar to type I neurofibromatosis. CASE REPORT: A 30-year-old man had more than 300 cutaneomucosal tumours. Most were sessile and of firm consistency on normal coloured skin. Histology reported masses of fusiform dermal cells S100 protein (+), NSE (-), actin (-). The cells had a polygonal ultrastructure with fine ramifications. Neurilemmomatosis (schwannomatosis) was diagnosed. No neurological or systemic disorder could be detected. The most bothersome tumors were destroyed. DISCUSSION: This is a typical anatomoclinical presentation of cutaneous neurilemmomatosis. This exceptional state raises the problem of differential diagnosis and nosological distinction from von Recklinhausen's disease. A characteristic feature in this case was the total absence of any malformation or associated tumour, notably neurological tumours. To our knowledge, this is the only documented case of disseminated neurilemmomatosis strictly limited to the skin.