Sculpting MHC class II-restricted self and non-self peptidome by the class I Ag-processing machinery and its impact on Th-cell responses.

Spencer CT, Dragovic SM, Conant SB, Gray JJ, Zheng M, Samir P, Niu X, Moutaftsi M, Van Kaer L, Sette A, Link AJ, Joyce S
Eur J Immunol. 2013 43 (5): 1162-72

PMID: 23386199 · PMCID: PMC3798073 · DOI:10.1002/eji.201243087

It is generally assumed that the MHC class I antigen (Ag)-processing (CAP) machinery - which supplies peptides for presentation by class I molecules - plays no role in class II-restricted presentation of cytoplasmic Ags. In striking contrast to this assumption, we previously reported that proteasome inhibition, TAP deficiency or ERAAP deficiency led to dramatically altered T helper (Th)-cell responses to allograft (HY) and microbial (Listeria monocytogenes) Ags. Herein, we tested whether altered Ag processing and presentation, altered CD4(+) T-cell repertoire, or both underlay the above finding. We found that TAP deficiency and ERAAP deficiency dramatically altered the quality of class II-associated self peptides suggesting that the CAP machinery impacts class II-restricted Ag processing and presentation. Consistent with altered self peptidomes, the CD4(+) T-cell receptor repertoire of mice deficient in the CAP machinery substantially differed from that of WT animals resulting in altered CD4(+) T-cell Ag recognition patterns. These data suggest that TAP and ERAAP sculpt the class II-restricted peptidome, impacting the CD4(+) T-cell repertoire, and ultimately altering Th-cell responses. Together with our previous findings, these data suggest multiple CAP machinery components sequester or degrade MHC class II-restricted epitopes that would otherwise be capable of eliciting functional Th-cell responses.

© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

MeSH Terms (18)

Amino Acid Sequence Animals Antigen-Presenting Cells Antigen Presentation Antigens, Ly Epitopes Histocompatibility Antigens Class I Histocompatibility Antigens Class II Leucyl Aminopeptidase Membrane Proteins Mice Mice, Knockout Molecular Sequence Data Peptide Fragments Proteomics Sequence Analysis, Protein T-Lymphocytes, Helper-Inducer Tandem Mass Spectrometry

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