Published online
doi:10.1084/jem.20062610
The Journal of Experimental Medicine, Vol. 204, No. 11, 2747-2757
The Rockefeller University Press, 0022-1007 $30.00
© Yachi et al.
T cell activation enhancement by endogenous pMHC acts for both weak and strong agonists but varies with differentiation state
Pia P. Yachi,
Carina Lotz,
Jeanette Ampudia, and
Nicholas R.J. Gascoigne
Department of Immunology, The Scripps Research Institute, La Jolla, CA 92037
CORRESPONDENCE Nicholas R.J. Gascoigne: gascoigne{at}scripps.edu
T cells are extremely sensitive in their ability to find minute amounts of antigenic peptide in the midst of many endogenous peptides presented on an antigen-presenting cell. The role of endogenous peptides in the recognition of foreign peptide and hence in T cell activation has remained controversial for CD8+ T cell activation. We showed previously that in a CD8+ T cell hybridoma, nonstimulatory endogenous peptides enhance T cell sensitivity to antigen by increasing the coreceptor function of CD8. However, others were not able to detect such enhancement in naive and activated CD8+ T cells. Here, we show that endogenous peptides substantially enhance the ability of T cells to detect antigen, an effect measurable by up-regulation of activation or maturation markers and by increased effector function. This enhancement is most pronounced in thymocytes, moderate in naive T cells, and mild in effector T cells. The importance of endogenous peptides is inversely proportional to the agonist activity of the stimulatory peptide presented. Unlike for CD4+ T cells, the T cell receptor of CD8+ T cells does not distinguish between endogenous peptides for their ability to enhance antigen recognition.
Abbreviations used: APL, altered peptide ligand; cSMAC, central supramolecular activation cluster; DP, double-positive; IS, immunological synapse(s); Kb, H-2Kb; MFI, mean fluorescent intensity; pMHC, peptide–MHC; VSV, vesicular stomatitis virus.

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