Human blood mDC subsets exhibit distinct TLR repertoire and responsiveness

International audienceHuman blood DCs encompass pDCs and two subsets of mDCs: CD1c(+) mDCs and CD141(+) mDCs. The rare CD141(+) DC population is thought to be the equivalent of mouse CD8α(+) cDCs that play a significant role in antigen cross-presentation. Here, we analyzed by Q-PCR TLR1-10 expression in blood DC subsets. Whereas CD1c(+) DCs express all TLR except TLR9, CD141(+) DCs present a more restricted pattern with high expression of TLR3 and -10, expression of TLR1,-2, -6, and -8, and lack of TLR4, -5, -7, and -9. The in vitro analysis of isolated mDC subset reponsiveness to an extensive panel of TLR ligands confirmed these results, with CD141(+) DCs responding only to TLR1/2, -3, and -7/8. The cytokine/chemokine production profile of isolated CD141(+) DCs was also more restricted, as they produced mainly proinflammatory cytokines but no IL-12 and to a lower level, in comparison with CD1c(+) DCs, except for CXCL10, CCL5, and IFN-β. In contrast, with the use of a whole blood assay, we found that CD141(+) DCs produce IL-12 in response to TLR1/2, -3, and more surprisingly, -9. Finally, both mDC subsets are potent inducers of Th1 response, particularly after TLR3 triggering. Taken together, these data confirmed functional differences between blood mDC subsets. The major response of CD141(+) mDCs to TLR3 ligand and their cytokine production pattern suggest a role for these cells in antiviral immunity

Receptor activating NF-κB ligand (RANKL) is a constitutive intracellular protein in resting human basophils and is strongly induced on their surface by interleukin 3

International audienceReceptor activating NF-B ligand (RANKL) is a member of the TNF superfamily that plays a pivotal role in bone homeostasis as being the major osteoclastogenesis factor. RANKL also has pleiotropic effects in the immune system in which it is expressed by activated T and B cells and some innate lymphoid cells. RANKL-RANK interactions mediate lymph node organogenesis and immunoregulatory functions in autoimmune disease and carcinogenesis as well as cross talk between the immune system and bone. In this study, we show that basophils were the strongest RANKL mRNA-expressing cells amongst major leukocyte subsets in human blood. RANKL was preformed as an intracellular protein in resting basophils and was rapidly and strongly expressed on their surface upon stimulation with IL-3, but not other stimuli. This expression was stable for at least 6 days. Activated basophils could also release soluble RANKL in small quantities upon interaction with DCs or monocytes. In the blood, basophils were the sole cells to express membrane RANKL in response to IL-3. This study indicates that basophils should be considered as new players in the pleiotropic and complex RANKL-RANK interaction system and suggests a role for RANKL in the interaction between basophils and immune cells in inflammatory allergic tissues and secondary lymphoid organs

Persistent deficiency of circulating mucosal-associated invariant T (MAIT) cells in ANCA-associated vasculitis

International audienceObjective: 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

Newborn Screening for Severe Combined Immunodeficiency: Analytic and Clinical Performance of the T Cell Receptor Excision Circle Assay in France (DEPISTREC Study)

International audienceSevere combined immunodeficiency (SCID) is characterized by a major T cell deficiency. Infants with SCID are asymptomatic at birth but die from infections in the first year of life if not treated. Survival rates are better for early treatment. SCID therefore meets criteria for newborn screening (NBS). T cell receptor excision circle (TREC) quantification is a reliable marker of T cell deficiency and can be performed using Guthrie cards. The DEPISTREC project was designed to study the feasibility, clinical utility, and cost-effectiveness of generalized SCID screening in France. About 200,000 babies from all over the country were screened at birth with a commercial kit. We determined assay performance and proposed a cutoff for classification of results. Our findings suggest that, given clearly established validation rules and decision-making procedures, the TREC assay is a suitably specific and sensitive method for high-throughput SCID screening. Clinical Trials: NCT02244450

Serum pepsinogens can help to discriminate between H. pylori-induced and auto-immune atrophic gastritis: Results from a prospective multicenter study

International audienceBackground: Serum pepsinogen (PG) testing is recommended by the European guidelines for diagnosis of chronic atrophic gastritis (CAG). However, wide variations in diagnostic performances are observed, due to the differences in the extent of gastric atrophy, and possibly in its origin (Helicobacter pylori-, autoimmune (AIG)). Aim. To analyze the diagnostic performances of PGs testing according to these different parameters, using enzyme-linked-immunosorbent serologic assay (ELISA) and chemiluminescent immunoassay (CLEIA). Methods: Serum samples from patients having undergone gastroscopy with biopsies in five French centers were collected prospectively. Sensitivity (Se), specificity (Sp), and Area Under Curve were analyzed according to the extent and origin of CAG. Results: Overall, 344 patients (156 males [45%]; mean age 58.8 [±14.2] years) were included, among whom 44 had AIG. Diagnostic performances of PG I for the detection of corpus CAG were excellent, with Se and Sp of 92.7% and 99.1% for ELISA and 90.5% and 98.2% for CLEIA, respectively. For AIG, corresponding values were 97.7% and 97.4% for ELISA, and 95.6% and 97.1% for CLEIA. In multivariate analysis, PG levels were associated with the auto-immune origin (p<0.001) but not with the extent of the atrophic gastritis. Conclusions: Pepsinogens are highly efficient for the diagnosis of corpus-limited CAG and allow to discriminate AIG from H. pylori-induced gastritis