B Cell Activation by Outer Membrane Vesicles—A Novel Virulence Mechanism

PLoS Pathogens

Christer Larsson¹  Anne Månsson²  Lars-Olaf Cardell²  Johan Jendholm³  Kristian Riesbeck³  Maria Laura A. Perez Vidakovics³  Matthias Mörgelin⁴ 

[1] Center for Molecular Pathology, Department of Laboratory Medicine, University Hospital Malmö, Lund University, Malmö, Sweden;Division of ENT Diseases, Department of Clinical Sciences, Intervention and Technology, Karolinska Institute, Huddinge, Sweden;Medical Microbiology, Department of Laboratory Medicine, University Hospital Malmö, Lund University, Malmö, Sweden;Section of Clinical and Experimental Infectious Medicine, Department of Clinical Sciences, Lund University, Lund, Sweden

关键词: B cells;    Flow cytometry;    Immune receptor signaling;    Cell binding;    Lipids;    B cell receptors;    Deoxyribonucleases;    Cell staining;   

DOI  :  10.1371/journal.ppat.1000724

学科分类：生物科学（综合）

来源: Public Library of Science

【 摘 要 】

Secretion of outer membrane vesicles (OMV) is an intriguing phenomenon of Gram-negative bacteria and has been suggested to play a role as virulence factors. The respiratory pathogens Moraxella catarrhalis reside in tonsils adjacent to B cells, and we have previously shown that M. catarrhalis induce a T cell independent B cell response by the immunoglobulin (Ig) D-binding superantigen MID. Here we demonstrate that Moraxella are endocytosed and killed by human tonsillar B cells, whereas OMV have the potential to interact and activate B cells leading to bacterial rescue. The B cell response induced by OMV begins with IgD B cell receptor (BCR) clustering and Ca2+ mobilization followed by BCR internalization. In addition to IgD BCR, TLR9 and TLR2 were found to colocalize in lipid raft motifs after exposure to OMV. Two components of the OMV, i.e., MID and unmethylated CpG-DNA motifs, were found to be critical for B cell activation. OMV containing MID bound to and activated tonsillar CD19+ IgD+ lymphocytes resulting in IL-6 and IgM production in addition to increased surface marker density (HLA-DR, CD45, CD64, and CD86), whereas MID-deficient OMV failed to induce B cell activation. DNA associated with OMV induced full B cell activation by signaling through TLR9. Importantly, this concept was verified in vivo, as OMV equipped with MID and DNA were found in a 9-year old patient suffering from Moraxella sinusitis. In conclusion, Moraxella avoid direct interaction with host B cells by redirecting the adaptive humoral immune response using its superantigen-bearing OMV as decoys.

【 授权许可】

CC BY