The self-peptide repertoire plays a critical role in transplant tolerance induction
Eric T. Son, … , Nicole A. Mifsud, Alexandra F. Sharland
Eric T. Son, … , Nicole A. Mifsud, Alexandra F. Sharland
Published August 24, 2021
Citation Information: J Clin Invest. 2021;131(21):e146771. https://doi.org/10.1172/JCI146771.
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The self-peptide repertoire plays a critical role in transplant tolerance induction

Abstract

While direct allorecognition underpins both solid organ allograft rejection and tolerance induction, the specific molecular targets of most directly alloreactive CD8+ T cells have not been defined. In this study, we used a combination of genetically engineered major histocompatibility complex class I (MHC I) constructs, mice with a hepatocyte-specific mutation in the class I antigen-presentation pathway, and immunopeptidomic analysis to provide definitive evidence for the contribution of the peptide cargo of allogeneic MHC I molecules to transplant tolerance induction. We established a systematic approach for the discovery of directly recognized pMHC epitopes and identified 17 strongly immunogenic H-2Kb–associated peptides recognized by CD8+ T cells from B10.BR (H-2k) mice, 13 of which were also recognized by BALB/c (H-2d) mice. As few as 5 different tetramers used together were able to identify a high proportion of alloreactive T cells within a polyclonal population, suggesting that there are immunodominant allogeneic MHC-peptide complexes that can account for a large component of the alloresponse.

Authors

Eric T. Son, Pouya Faridi, Moumita Paul-Heng, Mario L. Leong, Kieran English, Sri H. Ramarathinam, Asolina Braun, Nadine L. Dudek, Ian E. Alexander, Leszek Lisowski, Patrick Bertolino, David G. Bowen, Anthony W. Purcell, Nicole A. Mifsud, Alexandra F. Sharland

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Figure 9

Features of immunogenic pMHC recognized by mice from different allogeneic backgrounds.

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Features of immunogenic pMHC recognized by mice from different allogenei...
(A) One hundred peptides were screened for recognition by activated alloreactive T cells. T cells from female B10.BR mice primed with a female 178.3 skin graft and male BALB/c mice primed with a male C57BL/6 skin graft were used in parallel with T cells from primed male B10.BR. A heatmap was generated in order to compare recognition of pMHC epitopes across different sexes and strains. Epitopes are ordered from the top to the bottom by the average of pMHC tetramer binding across all samples. Thirteen pMHCs were recognized by more than 5% of activated alloreactive T cells across all 3 groups. Full peptide screening data can be found in Supplemental Table 4. (B) Strong correlation of T cell binding to each pMHC was found between male and female B10.BR (Pearson correlation coefficient, r = 0.76, P < 0.0001) and between male B10.BR and male BALB/c (r = 0.62, P < 0.0001). (C) For male B10.BR mice, the proportion of T cells binding 8-mer pMHC tetramers was proportional to log10 of the product of the spectral intensity values for each peptide across 3 different tissues (r = 0.52, P < 0.0001). Conversely, binding to 9-mer pMHC tetramers did not correlate with peptide spectral intensity (r = 0.059, P = 0.65). For each pMHC epitope, data were obtained from 1 to 2 independent experiments with a total of 3 biological replicates. (D) Predicted peptide binding affinity for H-2Kb (measured by IC50) did not differ significantly between strongly, moderately, or nonimmunogenic peptides (P = 0.098 by 1-way ANOVA, mean ± SEM are shown), (E) nor was a correlation observed between IC50 and spectral intensity values (r = 0.11, P = 0.34).