Dynamics of Major Histocompatibility Complex Class II Compartments during B Cell Receptor–mediated Cell Activation

Antigen recognition by clonotypic B cell receptor (BcR) is the first step of B lymphocytes differentiation into plasmocytes. This B cell function is dependent on efficient major histocompatibility complex (MHC) class II–restricted presentation of BcR-bound antigens. In this work, we analyzed the subcellular mechanisms underlying antigen presentation after BcR engagement on B cells. In quiescent B cells, we found that MHC class II molecules mostly accumulated at the cell surface and in an intracellular pool of tubulovesicular structures, whereas H2-M molecules were mostly detected in distinct lysosomal compartments devoid of MHC class II. BcR stimulation induced the transient intracellular accumulation of MHC class II molecules in newly formed multivesicular bodies (MVBs), to which H2-M was recruited. The reversible downregulation of cathepsin S activity led to the transient accumulation of invariant chain–MHC class II complexes in MVBs. A few hours after BcR engagement, cathepsin S activity increased, the p10 invariant chain disappeared, and MHC class II–peptide complexes arrived at the plasma membrane. Thus, BcR engagement induced the transient formation of antigen-processing compartments, enabling antigen-specific B cells to become effective antigen-presenting cells

A Critical Role for Syk Protein Tyrosine Kinase in Fc Receptor-Mediated Antigen Presentation and Induction of Dendritic Cell Maturation

AbstractDendritic cells (DCs) are the only APCs capable of initiating adaptive immune responses. The initiation of immune responses requires that DCs 1) internalize and present Ags; and 2) undergo a differentiation process, called "maturation", which transforms DCs into efficient APCs. DC maturation may be initiated by the engagement of different surface receptors, including certain cytokine receptors (such as TNFR), Toll-like receptors, CD40, and FcRs. The early activation events that link receptor engagement and DC maturation are not well characterized. We found that FcR engagement by immune complexes induced the phosphorylation of Syk, a protein tyrosine kinase acting immediately downstream of FcRs. Syk was dispensable for DC differentiation in vitro and in vivo, but was strictly required for immune complexes internalization and subsequent Ag presentation to T lymphocytes. Importantly, Syk was also required for the induction of DC maturation and IL-12 production after FcR engagement, but not after engagement of other surface receptors, such as TNFR or Toll-like receptors. Therefore, protein tyrosine phosphorylation by Syk represents a novel pathway for the induction of DC maturation

The actin-based motor protein myosin II regulates MHC class II trafficking and BCR-driven antigen presentation

Antigen (Ag) capture and presentation onto major histocompatibility complex (MHC) class II molecules by B lymphocytes is mediated by their surface Ag receptor (B cell receptor [BCR]). Therefore, the transport of vesicles that carry MHC class II and BCR–Ag complexes must be coordinated for them to converge for processing. In this study, we identify the actin-associated motor protein myosin II as being essential for this process. Myosin II is activated upon BCR engagement and associates with MHC class II–invariant chain complexes. Myosin II inhibition or depletion compromises the convergence and concentration of MHC class II and BCR–Ag complexes into lysosomes devoted to Ag processing. Accordingly, the formation of MHC class II–peptides and subsequent CD4 T cell activation are impaired in cells lacking myosin II activity. Therefore, myosin II emerges as a key motor protein in BCR-driven Ag processing and presentation

Modifications après activation cellulaire des caractéristiques morphologiques et biochimiques des compartiments de maturation des molécules du complexe majeur d'histocompatibilité de classe II dans les lymphocytes B et un modèle de mastocytes muqueux (les RBL-2H3)

PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF

Wiedergewinnung verlorener Schrift und Analyse der Tintenzusammensetzung der beglaubigten Kopie der Handelsprivilegien Hamburgs, Threse B 15 a (von 14.Juli 1482), Bibliothek des Staatsarchives, Hamburg

Conference poster. Conference: "Archäometrie und Denkmalpflege 2018" DESY, Hamburg Multispectral Imaging and X-Ray Fluorescence in Ink Analysis and recovery of lost writing, Threse B 15 a (von 14.Juli 1482), Bibliothek des Staatsarchives, Hamburg An authentic copy of a certificate of trade privileges issued by the Kaiser Friedrich the third on 14th of July 1482 to the mayor and council of Hamburg, was analyzed. The certificate, which is stored at the state archive in Hamburg, regards regulations for shipping commercial goods on the Elbe river. This document confirms that no goods like rye, wheat, barley and other grains, as well as wine and beer, could be shipped past Hamburg’s harbor and that they had to be unloaded and traded in Hamburg instead. It also withdraws the previously granted trade privilege to Lord of Barby, also located on the Elbe river, south of Magdeburg, to ship goods past Hamburg’s harbor without paying a customs fee. Unfortunately, the legibility of the certificate of privileges is impeded locally due to severe mold damage, as the document was stored in a cold humid room. We present complementary results of ink investigation and text recovery performed by MSI and XRF techniques. Supplementary data can be found here: Multispectral Imaging Data X-Ray Fluorescence Dat