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Introduction Le dosage des chaines legeres libres Kappa dans le liquide cerebrospinal (LCS) et le calcul de l’index kappa semble apporter une aide interessante au diagnostic biologique de la sclerose en plaques. Objectifs Les etudes precedemment publiees fournissent des cut-offs variables pour le quotient Kappa et l’index Kappa. Nous presentons ici les resultats de l’application de ces differents cut-offs sur les resultats des mesures obtenues au laboratoire. Patients et methodes Nous avons mesure retrospectivement sur 236 couples serums-LCS les parametres suivants : albumine, IgG, IgA, IgM, chaines legeres libres Kappa et chaines legeres libres lambda. Tous les dosages ont ete realises sur Optilite® (Binding Site, Birmingham, Royaume-Uni) avec des reactifs dedies. Nous avons calcule les differents rapports et index. Parmi les 236 couples serums-LCS analyses, on retrouvait a l’IEF la presence de bandes oligoclonales (BOC) d’IgG dans 91 cas et l’absence de BOC dans 145 cas. Resultats Les resultats des dosages ont ete analyses selon la presence (BOC +) ou l’absence (BOC −) de synthese locale intrathecale d’IgG mise en evidence a l’IEF. On note des concentrations de chaines legeres Kappa, un quotient Kappa et surtout un index Kappa significativement plus eleve (p Discussion En appliquant pour l’index Kappa les differents cut-off de 2,9 ; 4,3 ou 5,8, nous obtenons une sensibilite variant de 100 % a 96 %, une specificite de 54 % a 71 %, une valeur predictive positive (VPP) variant de 86 % a 91 % et une valeur predictive negative (VPN) variant de 100 % a 87 %. Conclusion Dans notre etude le cut-off le plus sensible pour l’index IgG est celui determine par Valencia-Vera, c’est egalement celui qui nous fournit la meilleure VPN.

International audience; Objective: Mucosal associated invariant T cells (MAIT) and innate lymphoid cells (ILCs) have immuno-regulatory functions at mucosal sites and have been involved in various inflammatory and autoimmune diseases. The aim of this study was to assess their frequencies in blood in ANCA-associated vasculitis (AAV).Methods: The frequencies and function of MAIT cells, ILCs, gdT, iNKT, NK cells were analyzed by flow cytometry on PBMC of patients with granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA) without any treatment, in acute (AP) and remission phase (RP) and compared with healthy controls (HC).Results: The frequencies of MAIT cells were strongly decreased in GPA and MPA in AP compared to HC, both in never treated and in relapsing patients and independently of patient age. This was associated with an activated phenotype of patient MAIT cells, as shown by increased expression of CD69 and IFNg. MAIT cells remained decreased during RP in AAV patients. The frequencies of iNKT and gdT cells were unaffected compared to HC, whereas those of NK cells were slightly reduced during AP in MPA. We also observed a significant decrease in frequencies of total ILCs with decreased ILC2 and ILC3 and increased ILC1 during AP in both GPA and MPA compared to HC. These frequencies normalized during RP. Interestingly , we observed a significant correlation between the frequency of total ILCs and BVAS.Conclusion: We show for the first time that AAV are associated with a major decrease and an activated phenotype of blood MAIT cell. These features persisted during remission suggesting a role for MAIT cells in the pathogenesis of AAV.