Contrasting cytoskeletal regulation of MHC class II peptide presentation by human B cells or dendritic cells

Eur J Immunol. 2008 Apr;38(4):1096-105. doi: 10.1002/eji.200737455.


MHC class II-mediated antigen presentation by B lymphocytes or dendritic cells (DC) initiates CD4+ T lymphocyte activation. In B lymphocytes, MHC class II peptide presentation has been characterised by recruitment of MHC class II, F-actin and lipid rafts to the B cell-T cell immunological synapse. We now show that MHC class II engagement in B lymphocytes induced lipid raft-independent Rho and Rac activation and that inhibition of either Rho-GTPase activation or actin polymerisation in the B cell abrogated T cell activation without altering B cell-T cell conjugate formation. Short-hairpin RNA studies excluded a role for the Cdc42 effector Wiskott-Aldrich syndrome protein. In contrast, antigen presentation by DC was Rho-GTPase-independent although actin was recruited to the DC-T cell interaction site. Moreover, actin depolymerisation in the DC significantly increased T cell activation without altering the number of DC-T cell conjugates. Finally we show that stable recruitment of HLA-DR to the site of the immunological synapse is not a uniform observation in DC and demonstrate reduced HLA-DR expression at the site of microtubule organising centre polarization. Therefore although actin accumulates in DC and B lymphocytes at the immunological synapse with antigen-specific T lymphocytes, this does not reflect comparable functional roles of their actin cytoskeletons in antigen presentation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actins / metabolism
  • Antigen Presentation / immunology
  • B-Lymphocytes / immunology*
  • Cell Communication / immunology
  • Cells, Cultured
  • Cytoskeleton / immunology*
  • Dendritic Cells / immunology*
  • Enzyme Activation
  • Histocompatibility Antigens Class II / immunology*
  • Humans
  • Membrane Microdomains / immunology
  • Membrane Microdomains / metabolism
  • Peptides / immunology*
  • Wiskott-Aldrich Syndrome Protein / genetics
  • Wiskott-Aldrich Syndrome Protein / metabolism
  • rac GTP-Binding Proteins / metabolism
  • rho GTP-Binding Proteins / metabolism


  • Actins
  • Histocompatibility Antigens Class II
  • Peptides
  • Wiskott-Aldrich Syndrome Protein
  • rac GTP-Binding Proteins
  • rho GTP-Binding Proteins