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Visualizing Antigen Specific CD4+ T Cells using MHC Class II Tetramers
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The tetraspanin CD9 mediates lateral association of MHC class II molecules on the dendritic cell surface

Julia J Unternaehrer1, Amy Chow, Marc Pypaert

  • 1Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520-8002, USA.

Proceedings of the National Academy of Sciences of the United States of America
|December 28, 2006
PubMed

Insights

Dendritic cells (DCs) organize MHC class II (MHC II) molecules through interactions mediated by CD9. This CD9-dependent clustering of MHC II on DCs enhances T cell receptor stimulation.

Area of Science:

  • Immunology
  • Cell Biology
  • Molecular Biology

Background:

  • MHC class II (MHC II) molecules are crucial for antigen presentation.
  • The organization of MHC II on the plasma membrane of antigen-presenting cells influences immune responses.
  • Dendritic cells (DCs) and B cells are key antigen-presenting cells.

Purpose of the Study:

  • To investigate the distinctive organization of MHC II molecules on the dendritic cell (DC) plasma membrane.
  • To identify the molecular mechanisms underlying MHC II lateral interactions on DCs.
  • To determine the role of CD9 in MHC II organization and function.

Main Methods:

  • Analysis of MHC II molecular organization in DC lysates and on live cell surfaces.
  • Co-precipitation assays to assess molecular interactions.
  • Studies using CD9-deficient (CD9(-/-)) mice DCs and B cells expressing exogenous CD9.

Main Results:

  • MHC II molecules (I-A and I-E) exhibit lateral interactions on DCs, unlike on B blasts.
  • These interactions are dependent on the tetraspanin CD9, not solely on surface density.
  • CD9 mediates the association of heterologous MHC II molecules, facilitating multimer formation.

Conclusions:

  • CD9 is essential for the association of heterologous MHC II molecules on DCs.
  • This CD9-driven MHC II clustering is a specialization of DCs.
  • The formation of MHC II multimers enhances T cell receptor stimulation by DCs.

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