IMMUNOLOGY T cells Masquerading as Antigen-Presenting Cells

Activation of T cells is normally promoted by interaction of T cell receptors with complexes of antigenic peptide bound to MHC (major histocompatibility complex) proteins on the surface of antigen-presenting cells (APCs). However, Ge et al. report that activation of naïve or CD8⁺ T cells can occur with exposure to soluble peptide-MHC complexes in the absence of APCs. Their results indicated that activation actually occurred through transfer of peptides to MHC molecules expressed by the T cells. Thus, T cells were only activated if they expressed the same MHC as the one with which they were stimulated. Furthermore T cells that had been exposed to MHC-peptide monomers and then washed could subsequently activate naïve T cells, apparently by presenting the peptide antigen on their cell surface as would a professional APC. Given that soluble peptide-MHC complexes are likely to exist in serum or synovial fluid, the authors propose that such presentation of antigen by T cells in vivo could influence T cell maturation.

Q. Ge, J. D. Stone, M. T. Thompson, J. R. Cochran, M. Rushe, H. N. Eisen, J. Chen, L. J. Stern, Soluble peptide-MHC monomers cause activation of CD8⁺ T cells through transfer of the peptide to T cell MHC molecules. Proc. Natl. Acad. Sci. U.S.A. 99, 13729-13734 (2002). [Abstract] [Full Text]

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VIRTUAL JOURNAL
Soluble peptide-MHC monomers cause activation of CD8⁺ T cells through transfer of the peptide to T cell MHC molecules

Qing Ge, Jennifer D. Stone, M. Todd Thompson, Jennifer R. Cochran, Mia Rushe, Herman N. Eisen, Jianzhu Chen, and Lawrence J. Stern (15 October 2002)
PNAS 99 (21), 13729. [DOI: 10.1073/pnas.212515299]
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