The impact of TCR-binding properties and antigen presentation format on T cell responsiveness.
TCR interactions with cognate peptide-MHC (pepMHC) ligands are generally low affinity. This feature, together with the requirement for CD8/CD4 participation, has made it difficult to dissect relationships between TCR-binding parameters and T cell activation. Interpretations are further complicated when comparing different pepMHC, because these can vary greatly in stability. To examine the relationships between TCR-binding properties and T cell responses, in this study we characterized the interactions and activities mediated by a panel of TCRs that differed widely in their binding to the same pepMHC. Monovalent binding of soluble TCR was characterized by surface plasmon resonance, and T cell hybridomas that expressed these TCR, with or without CD8 coexpression, were tested for their binding of monomeric and oligomeric forms of the pepMHC and for subsequent responses (IL-2 release). The binding threshold for eliciting this response in the absence of CD8 (K(D) = 600 nM) exhibited a relatively sharp cutoff between full activity and no activity, consistent with a switchlike response to pepMHC on APCs. However, when the pepMHC was immobilized (plate bound), T cells with the lowest affinity TCRs (e.g., K(D) = 30 microM) responded, even in the absence of CD8, indicating that these TCR are signaling competent. Surprisingly, even cells that expressed high-affinity (K(D) = 16 nM) TCRs along with CD8 were unresponsive to oligomers in solution. The findings suggest that to drive downstream T cell responses, pepMHC must be presented in a form that supports formation of appropriate supramolecular clusters.
Chervin
Adam S
AS
Department of Biochemistry, University of Illinois, Urbana, IL 61801, USA.
Stone
Jennifer D
JD
Holler
Phillip D
PD
Bai
Ailin
A
Chen
Jianzhu
J
Eisen
Herman N
HN
Kranz
David M
DM
D000818:Animals; D017951:Antigen Presentation; D000938:Antigen-Presenting Cells; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D006825:Hybridomas; D008024:Ligands; D051379:Mice; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry* / Q000276:immunology*; D011485:Protein Binding / Q000276:immunology; D011948:Receptors, Antigen, T-Cell / Q000276:immunology*; D020349:Surface Plasmon Resonance; D013601:T-Lymphocytes / Q000276:immunology*
D008024:Ligands; D010455:Peptides; D011948:Receptors, Antigen, T-Cell