CD40 ligand and MHC class II expression are essential for human peripheral B cell tolerance

Hyper-IgM (HIGM) syndromes are primary immunodeficiencies characterized by defects of class switch recombination and somatic hypermutation. HIGM patients who carry mutations in the CD40-ligand (CD40L) gene expressed by CD4+ T cells suffer from recurrent infections and often develop autoimmune disorders. To investigate the impact of CD40L–CD40 interactions on human B cell tolerance, we tested by ELISA the reactivity of recombinant antibodies isolated from single B cells from three CD40L-deficient patients. Antibody characteristics and reactivity from CD40L-deficient new emigrant B cells were similar to those from healthy donors, suggesting that CD40L–CD40 interactions do not regulate central B cell tolerance. In contrast, mature naive B cells from CD40L-deficient patients expressed a high proportion of autoreactive antibodies, including antinuclear antibodies. Thus, CD40L–CD40 interactions are essential for peripheral B cell tolerance. In addition, a patient with the bare lymphocyte syndrome who could not express MHC class II molecules failed to counterselect autoreactive mature naive B cells, suggesting that peripheral B cell tolerance also depends on major histocompatibility complex (MHC) class II–T cell receptor (TCR) interactions. The decreased frequency of MHC class II–restricted CD4+ regulatory T cells in CD40L-deficient patients suggests that these T cells may mediate peripheral B cell tolerance through CD40L–CD40 and MHC class II–TCR interactions

Bases moléculaires du recrutement de l'inositol-phosphatase SHIP1 par les RFcgammaIIB, des récepteurs inhibiteurs de l'activation des lymphocytes B

PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

The SH2 domain-containing inositol 5-phosphatase SHIP1 is recruited to the intracytoplasmic domain of human FcgammaRIIB and is mandatory for negative regulation of B cell activation.

Murine FcgammaRIIB were demonstrated to recruit SH2 domain-containing inositol 5-phosphatases (SHIP1/2), when their ITIM is tyrosyl-phosphorylated upon co-aggregation with BCR, and SHIP1 to account for FcgammaRIIB-dependent negative regulation of murine B cell activation. Although human FcgammaRIIB share the same ITIM as murine FcgammaRIIB and similarly inhibit human B cell activation, which among the four known SH2 domain-containing (tyrosine or inositol) phosphatases is/are recruited by human FcgammaRIIB is unclear. Our recent finding that, besides the ITIM, a second tyrosine-based motif is mandatory for murine FcgammaRIIB to recruit SHIP1 challenged the possibility that human FcgammaRIIB recruit this phosphatase. Human FcgammaRIIB indeed lack this motif. Using an experimental model which enabled us to compare human FcgammaRIIB and murine FcgammaRIIB under strictly controlled conditions, we show that SHIP1 is recruited to the intracytoplasmic domain of human FcgammaRIIB and inhibits the same biological responses and intracellular signals as when recruited by murine FcgammaRIIB. Identical results were observed in murine and in human B cells. We demonstrate that SHIP is necessary for human FcgammaRIIB to inhibit BCR signaling, and cannot be replaced by SHP-1 or SHP-2. Although it contains no tyrosine, the C-terminal segment of human FcgammaRIIB was as mandatory as the tyrosine-containing C-terminal segment of murine FcgammaRIIB for SHIP1 to be recruited to the ITIM. This segment, however, did not recruit the adapters Grb2/Grap which were demonstrated to stabilize the recruitment of SHIP1 to the ITIM in murine FcgammaRIIB

Linker for activation of T cells integrates positive and negative signaling in mast cells.

International audienceThe transmembrane adapter linker for activation of T cells (LAT) is thought to couple immunoreceptors to intracellular signaling pathways. In mice, its intracytoplasmic domain contains nine tyrosines which, when phosphorylated upon receptor aggregation, recruit Src-homology 2 domain-containing cytosolic enzymes and adapters. The four distal tyrosines are critical for both TCR and FcepsilonRI signaling. Unexpectedly, knock-in mice expressing LAT with a point mutation of the first or of the last three of these tyrosines exhibited an abnormal T cell development characterized by a massive expansion of TH2-like alphabeta or gammadelta T cells, respectively. This phenotype suggests that, besides positive signals, LAT might support negative signals that normally regulate terminal T cell differentiation and proliferation. We investigated here whether LAT might similarly regulate mast cell activation, by generating not only positive but also negative signals, following FcR engagement. To this end, we examined IgE- and/or IgG-induced secretory and intracellular responses of mast cells derived from knock-in mice expressing LAT with combinations of tyrosine mutations (Y136F, Y(175, 195, 235)F, or Y(136, 175, 195, 235)F). A systematic comparison of pairs of mutants enabled us to dissect the respective roles played by the five proximal and the four distal tyrosines. We found that LAT tyrosines differentially contribute to exocytosis and cytokine secretion and differentially regulate biological responses of mucosal- and serosal-type mast cells. We also found that, indeed, both positive and negative signals may emanate from distinct tyrosines in LAT, whose integration modulates mast cell secretory responses

Mid-p strategy versus ITV strategy in locally advanced lung cancer. A randomized phase II study

International audiencePurpose/Objective The overall survival (OS) of patients (pts) with non-resectable locally advanced non-small cell lung carcinoma (LA-NSCLC) is poor, in part due to insufficient local control (LC) using conformal irradiation techniques (RT). The personalization of the RT margins may impact the LC and the outcome. Internal Target Volume strategy (ITV) versus "Mid-position" strategy (Mid-p), was compared in a prospective non-comparative randomized monocentric phase II trial in NSCLC patients treated by definitive radiotherapy. Planning Target volumes and mean lung dose were previously reported as significantly reduced using the Mid-p strategy (DOI: 10.1259/bjr.20190692). We report here the clinical results. Material and Methods Eligible patients were randomized (2:1) to be treated with Mid-p or ITV strategies. Patients with proven LA-NSCLC, non-resected, non-metastatic treated by definitive RT could be included. The main objective was to evaluate the 1-year progression-free-survival (PFS) rate in the two arms. 36 pts were planned in the Mid-p arm, Fleming single-stage design (1-sided =0.1, 80% power, P0=30%, P1=50%). Secondary objectives were to evaluate 1-y and 2-y LC, OS and acute/middle term toxicity (NCI-CTCAE v4).Results 54 pts were randomized from 09/12 to 05/18. 3 patients finally did not receive radiotherapy and were excluded from the analysis. Median age was 65.2 y, 2/3 of the patients were male and had IIIA NSCLC stages, 31% received concomitant chemotherapy. 34 pts and 17 pts were included in the analysis in the Mid-p arm and ITV arm respectively. Median RT dose was 66 Gy in the Mid-p arm and 62 Gy in the ITV arm. Median PFS were 9.3 months and 10.3 months in the Mid-p arm and ITV arms respectively. 1-year PFS rate were 38% (1-sided CI95% = 25-) and 47% (CI95% = [27;[) in the Mid-p/ITV arm respectively. Efficacy in Mid-p arm is below that expected (starting hypothesis p0=30%, p1=50%). 2-year PFS rates were 15% (Mid-p) and 12% (ITV). 2-years LC rates were 65% (CI95% [48;81]) and 76% (CI95% [53;94]) in the Mid-p/ITV arms respectively. The analysis of the type of local failures (in field versus border of fields) is under analysis and will be available for the congress.No grade 4 or toxic deaths related to RT were reported. Grade 3 acute lung toxicity were reported in 12% and 23% in Mid-p and in ITV arms respectively. Grade 2 and Grade 3 late radiation fibrosis were reported in 29% and 15% respectively in the Mid-p arm, versus 23% and 29% using ITV strategy. Conclusion Two-year LC and PFS in LA-NSCLC seems similar in this non comparative Phase II randomized study using Mid-p or ITV strategies. The details of local relapses regarding RT fields and margins are under analysis and will be presented during the congress.Conflict of interest: this study was granted by Elekta

The PTPN22 allele encoding an R620W variant interferes with the removal of developing autoreactive B cells in humans

Protein tyrosine phosphatase nonreceptor type 22 (PTPN22) gene polymorphisms are associated with many autoimmune diseases. The major risk allele encodes an R620W amino acid change that alters B cell receptor (BCR) signaling involved in the regulation of central B cell tolerance. To assess whether this PTPN22 risk allele affects the removal of developing autoreactive B cells, we tested by ELISA the reactivity of recombinant antibodies isolated from single B cells from asymptomatic healthy individuals carrying one or two PTPN22 risk allele(s) encoding the PTPN22 R620W variant. We found that new emigrant/transitional and mature naive B cells from carriers of this PTPN22 risk allele contained high frequencies of autoreactive clones compared with those from non-carriers, revealing defective central and peripheral B cell tolerance checkpoints. Hence, a single PTPN22 risk allele has a dominant effect on altering autoreactive B cell counterselection before any onset of autoimmunity. In addition, gene array experiments analyzing mature naive B cells displaying PTPN22 risk allele(s) revealed that the association strength of PTPN22 for autoimmunity may be due not only to the impaired removal of autoreactive B cells but also to the upregulation of genes such as CD40, TRAF1, and IRF5, which encode proteins that promote B cell activation and have been identified as susceptibility genes associated with autoimmune diseases. These data demonstrate that early B cell tolerance defects in autoimmunity can result from specific polymorphisms and precede the onset of disease

Identification of B lymphocytes specific for HA from A and B influenza strains in <i>ex vivo</i> PBMCs samples.

<p>PBMCs from different anonymous blood donors were pre-incubated with vaccine mono-bulk subunits from the B/Brisbane/60/2008 (B/HA pretreatment), or the H3N2 A/Panama/2007/1999 strain (A/HA pretreatment) and then stained HSA, rH3 (from A/Brisbane/10/2007), rH1 (from A/California/07/2009), or B/HA (from B/Brisbane/60/2008), as indicated. <b>A.</b> Staining pattern observed on CD20⁺ cells in PBMCs stained with the different rHA bait. The rectangular gates identify brilliant HA+ B-cells; the dotted vertical lines mark the gates used to sort HA⁺ B-cells for the ELISPOT assays. <b>B.</b> Expression of the CD27 memory marker on HA⁺ and HA^neg B cells identified based on the sorting gates. <b>C.</b> H3⁺ (n = 15,234), H1⁺ (n = 6482) and B/HA⁺ (n = 26,803) B-cells identified in A were sorted, mixed with autologous CD20^neg cells (in the ratio of 1∶20, 1∶100 and 1∶33) and activated with CpG and IL-2 for 5 days <i>in vitro</i>. Unsorted PBMCs and CD20^neg cells mixed with HA^neg B cells were also cultured in the same manner, as controls. After 5 days cultured cells were harvested and assayed by ELISPOT for the number of cells secreting IgG and IgG specific for mono-bulk subunits from the vaccine strain homologous to the sorting bait. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0070620#s2" target="_blank">Results</a> are expressed as numbers of antibody secreting cells (ASC) normalized to 10⁶ cultured cells assayed by ELISPOT. Nd indicates undetectable ASC.</p

Molecular cloning of HA⁺ B lymphocytes.

<p>PBMCs from 4 anonymous blood bank donors were stained as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0070620#pone-0070620-g004" target="_blank">Figure 4B</a>. Single H1⁺, H3⁺, or H1^negH3^neg CD20⁺ B-cells were sorted to perform molecular cloning and analysis of their paired V_HV_L Ig regions as described in Material and Methods section. <b>A–E.</b> Distribution of V_H (A), D_H (B), J_H (C), V_k (D) and J_k (E) gene use across arrays of B-cells sorted from each donor (16 and 18 HA⁺ clones from donors #1 and #2; 35 HA⁺ and 20 HA^neg clones from donor 3; 16 HA⁺ and 16 HA^neg clones from donor #4. <b>F–I.</b> Number of mutations in H1⁺ and H1^neg CD20⁺ B-cells from donors #3 and #4, which cause dissimilar (F, H) or similar (G, I) amino acid substitutions in V_H (G,I) and V_L (F,H). NS and ** indicate not significant, or significant (p<0.036) difference between mean numbers of mutations by one-way Wilcoxon non-parametric test.</p

H1⁺ IgG⁺ MBCs frequencies measured by flow-cytometry and by ELISPOT correlated linearly.

<p><b>A–B.</b> Specificity of the staining with the rH1 bait from A/Solomon Island/3/06. PBMCs (1.6×10⁸) from anonymous blood donors were stained with Live/Dead, incubated with an H3N2 mono-bulk vaccine subunit (from A/Panama/2007/1999), and then stained with Alexa647-conjugated HSA (6×10⁷), or Alexa647-conjugated rH1 (1×10⁸), and with an antiCD20 mAb. <b>A.</b> Binding pattern of HSA (A647-HSA; left panel) and of rH1 (A647-rH1; right panel) in the CD20⁺ B-cell gates. <b>B.</b> H1⁺ B-cells identified in A were sorted (n = 8215), mixed with autologous CD20^neg cells in the ratio of 1∶50 and activated with CpG and IL-2 for 5 days <i>in vitro</i>. Unsorted PBMC and CD20^neg cells were also cultured in the same manner as controls. After 5 days, equal numbers of cultured cells were harvested and assayed by ELISPOT for numbers of cells secreting IgG and IgG specific for H1N1 (from A/Solomon Island/3/06). <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0070620#s2" target="_blank">Results</a> are expressed as number of antibody secreting cells (ASC) normalized to 10⁶ cultured cells assayed by ELISPOT. Nd indicates undetectable ASC. <b>C.</b> Distribution of IgG⁺ B-cells among H1^neg and H1⁺ B cells expressing or not the CD27 B cell memory marker; shown is one representative subject. <b>D.</b> Replicates of frozen PBMCs from 4 anonymous blood donors were assayed by conventional ELISPOT, or incubated with an H3N2 mono-bulk vaccine subunit and stained with rH1, and anti-CD20 plus anti-human IgG antibodies. The scatter plot depicts paired values of H1⁺ IgG⁺ B-cell frequencies measured by flow-cytometry (y-axis) and by ELISPOT (x-axis) across three different experimental sessions. Shown are: the regression line with the related 95% confidence interval (gray areas), slope, intercepts, R² and p-value. <b>E.</b> Variability plot showing mean standard deviations of the measurements done by ELISPOT and flow-cytometry. The three dotted lines mark the grand mean and the upper and lower control limits.</p