[Next generation sequencing : a diagnostic tool for inherited immune defects]. / Séquençage à haut débit : outil de diagnostic des déficits immunitaires héréditaires.

Establishing the definitive diagnosis in the case of inherited immune defects (IID) is often challenging because the clinical features can be heterogeneous, atypical and overlapping different disease entities. The next generation sequencing technology (NGS) allows identifying genetic variants that are responsible for the observed clinical presentations. The use of NGS applied to the genes mutated in IIDs or known to be involved in the development, differentiation and regulation of the immune system allows to target hundreds of relevant genes in well characterized patients suspected of carrying inherited immune defects. This approach answers both diagnostic and research needs, facilitates the understanding of the mechanisms that underlie IIDs, and ultimately leads to the discovery of new therapeutic targets.

Etablir un diagnostic précis est souvent difficile dans le cas des déficits immunitaires héréditaires (DIH) car les manifestations cliniques sont hétérogènes et parfois atypiques ou communes à des maladies distinctes. Le séquençage à haut débit, aussi appelé next generation sequencing (NGS), permet d'identifier des variants génétiques responsables de caractéristiques cliniques. Le recours au NGS pour découvrir les gènes mutés dans les DIH ou connus pour être impliqués dans le développement, la différenciation et la régulation du système immunitaire, permet de cibler des centaines de gènes d'intérêt sur des patients suspectés de DIH pour lesquels le tableau clinique est documenté. Cette approche répond à la fois à des besoins de diagnostic et de recherche pour comprendre les mécanismes qui régissent les DIH et découvrir de nouveaux outils ou cibles thérapeutiques.

Capturing epidermal stemness for regenerative medicine.

The skin is privileged because several skin-derived stem cells (epithelial stem cells from epidermis and its appendages, mesenchymal stem cells from dermis and subcutis, melanocyte stem cells) can be efficiently captured for therapeutic use. Main indications remain the permanent coverage of extensive third degree burns and healing of chronic cutaneous wounds, but recent advances in gene therapy technology open the door to the treatment of disabling inherited skin diseases with genetically corrected keratinocyte stem cells. Therapeutic skin stem cells that were initially cultured in research or hospital laboratories must be produced according strict regulatory guidelines, which ensure patients and medical teams that the medicinal cell products are safe, of constant quality and manufactured according to state-of-the art technology. Nonetheless, it does not warrant clinical efficacy and permanent engraftment of autologous stem cells remains variable. There are many challenges ahead to improve efficacy among which to keep telomere-dependent senescence and telomere-independent senescence (clonal conversion) to a minimum in cell culture and to understand the cellular and molecular mechanisms implicated in engraftment. Finally, medicinal stem cells are expansive to produce and reimbursement of costs by health insurances is a major concern in many countries.

Critical role of WASp in germinal center tolerance through regulation of B cell apoptosis and diversification.

A main feature of Wiskott-Aldrich syndrome (WAS) is increased susceptibility to autoimmunity. A key contribution of B cells to development of these complications has been demonstrated through studies of samples from affected individuals and mouse models of the disease, but the role of the WAS protein (WASp) in controlling peripheral tolerance has not been specifically explored. Here we show that B cell responses remain T cell dependent in constitutive WASp-deficient mice, whereas selective WASp deletion in germinal center B cells (GCBs) is sufficient to induce broad development of self-reactive antibodies and kidney pathology, pointing to loss of germinal center tolerance as a primary cause leading to autoimmunity. Mechanistically, we show that WASp is upregulated in GCBs and regulates apoptosis and plasma cell differentiation in the germinal center and that the somatic hypermutation-derived diversification is the basis of autoantibody development.