The adaptor protein Bam32 in human dendritic cells participates in the regulation of MHC class I-induced CD8+ T cell activation

J Immunol. 2011 Oct 15;187(8):3972-8. doi: 10.4049/jimmunol.1003072. Epub 2011 Sep 19.


The B lymphocyte adaptor molecule of 32 kDa (Bam32) is strongly induced during the maturation of dendritic cells (DC). Most known functions of Bam32 are related to the signaling of the B cell receptor for Ag. Because DC do not express receptors specific for Ags, we aim at characterizing the role of Bam32 in human monocyte-derived DC in this study. Our results show that binding of allogeneic T cells to mature DC causes accumulation of Bam32 on the contact sites and that this translocation is mimicked by Ab-mediated engagement of MHC class I. Silencing of Bam32 in mature monocyte-derived DC results in an enhanced proliferation of CD8(+) T cells in an Ag-specific T cell proliferation assay. Further studies identify galectin-1 as an intracellular binding partner of Bam32. Regulating immune responses via regulatory T cell (Treg) modulation is one of the many immunological activities attributed to galectin-1. Therefore, we assayed mixed leukocyte reactions for Treg expansion and found fewer Treg in reactions stimulated with DC silenced for Bam32 compared to reactions stimulated with DC treated with a nontarget control. Based on our findings, we propose a role for Bam32 in the signaling of MHC class I molecules in professional Ag-presenting DC for the regulation of CD8(+) T cell activation. It is distinct from that of MHC class I recognized by CD8(+) T cells leading to target [corrected] cell death. Thus, our data pinpoint a novel level of T cell regulation that may be of biological relevance.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / immunology*
  • Adaptor Proteins, Signal Transducing / metabolism
  • Antigen Presentation / immunology
  • Blotting, Western
  • CD8-Positive T-Lymphocytes / immunology*
  • CD8-Positive T-Lymphocytes / metabolism
  • Cell Separation
  • Dendritic Cells / immunology*
  • Dendritic Cells / metabolism
  • Flow Cytometry
  • Histocompatibility Antigens Class I / immunology
  • Histocompatibility Antigens Class I / metabolism
  • Humans
  • Immunohistochemistry
  • Immunoprecipitation
  • Lymphocyte Activation / immunology*
  • Lymphocyte Culture Test, Mixed
  • Reverse Transcriptase Polymerase Chain Reaction
  • Two-Hybrid System Techniques


  • Adaptor Proteins, Signal Transducing
  • DAPP1 protein, human
  • Histocompatibility Antigens Class I