Standardized high-dimensional spectral cytometry protocol and panels for whole blood immune phenotyping in clinical and translational studies.

Flow cytometry is the method of choice for immunophenotyping in the context of clinical, translational, and systems immunology studies. Among the latter, the Milieu Intérieur (MI) project aims at defining the boundaries of a healthy immune response to identify determinants of immune response variation. MI used immunophenotyping of a 1000 healthy donor cohort by flow cytometry as a principal outcome for immune variance at steady state. New generation spectral cytometers now enable high-dimensional immune cell characterization from small sample volumes. Therefore, for the MI 10-year follow up study, we have developed two high-dimensional spectral flow cytometry panels for deep characterization of innate and adaptive whole blood immune cells (35 and 34 fluorescent markers, respectively). We have standardized the protocol for sample handling, staining, acquisition, and data analysis. This approach enables the reproducible quantification of over 182 immune cell phenotypes at a single site. We have applied the protocol to discern minor differences between healthy and patient samples and validated its value for application in immunomonitoring studies. Our protocol is currently used for characterization of the impact of age and environmental factors on peripheral blood immune phenotypes of >400 donors from the initial MI cohort.

Emerging therapy for improving wound repair of severe radiation burns using local bone marrow-derived stem cell administrations.

The therapeutic management of severe radiation burns remains a challenging issue today. Conventional surgical treatment including excision, skin autograft, or flap often fails to prevent unpredictable and uncontrolled extension of the radiation-induced necrotic process. In a recent very severe accidental radiation burn, we demonstrated the efficiency of a new therapeutic approach combining surgery and local cellular therapy using autologous mesenchymal stem cells (MSC), and we confirmed the crucial place of the dose assessment in this medical management. The patient presented a very significant radiation lesion located on the arm, which was first treated by several surgical procedures: iterative excisions, skin graft, latissimus muscle dorsi flap, and forearm radial flap. This conventional surgical therapy was unfortunately inefficient, leading to the use of an innovative cell therapy strategy. Autologous MSC were obtained from three bone marrow collections and were expanded according to a clinical-grade protocol using platelet-derived growth factors. A total of five local MSC administrations were performed in combination with skin autograft. After iterative local MSC administrations, the clinical evolution was favorable and no recurrence of radiation inflammatory waves occurred during the patient's 8-month follow-up. The benefit of this local cell therapy could be linked to the "drug cell" activity of MSC by modulating the radiation inflammatory processes, as suggested by the decrease in the C-reactive protein level observed after each MSC administration. The success of this combined treatment leads to new prospects in the medical management of severe radiation burns and more widely in the improvement of wound repair.