Potentiation of T Cell Stimulatory Activity by Chemical Fixation of a Weak Peptide-MHC Complex.
The stability of peptide-MHC complex (pMHC) is an important factor to shape the fate of peptide-specific T cell immune response, but how it influences on T cell activation process is poorly understood. To better understand that, we investigated various T cell activation events driven by LdMHCI loaded with graded concentrations of P2Ca and QL9 peptides, respectively, with 2C TCR Tg T cells; the binding strength of P2Ca for Ldis measurably weaker than that of QL9, but either peptides in the context of Ldinteract with 2C TCR with a similar strength. When their concentrations required for early T cell activation events, which occur within several minutes to an hour, were concerned, EC50s of QL9 were about 100 folds lower than those of P2Ca, which was expected from their association constants for Ld. When EC50s for late activation events, which takes over several hours to occur, were concerned, the differences grew even larger (> 300 folds), suggesting that, due to weak binding, Ld/P2Ca dissociate from each other more easily to lose its antigenicity in a short time. Accordingly, fixation of Ld/P2Ca with paraformaldehyde resulted in a significant improvement in its immunogenicity. These results imply that binding strength of a peptide for a MHC is a critical factor to determine the duration of pMHC-mediated T cell activation and thus the attainment of productive T cell activation. It is also suggested that paraformaldehyde fixation should be an effective tool to ameliorate the immunogenicity of pMHC with a poor stability.
Department of Chemistry and Chemical Biology, The Scripps Research Institute, La Jolla, California, USA.|College of Pharmacy, Chungnam National University, Daejeon 34134, Korea.
Inkyu
I
Hwang
Department of Chemistry and Chemical Biology, The Scripps Research Institute, La Jolla, California, USA.|College of Pharmacy, Dankook University, Yongin 16890, Korea.
Kwangmi
K
Kim
College of Pharmacy, Chungnam National University, Daejeon 34134, Korea.
Sojin
S
Choi
College of Pharmacy, Chungnam National University, Daejeon 34134, Korea.
Maria
M
Lomunova
D000199:Actins / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism; D006801:Humans; D008213:Lymphocyte Activation; D008285:Major Histocompatibility Complex / Q000276:immunology*; D051379:Mice; D008822:Mice, Transgenic; D010455:Peptides / Q000276:immunology*; D011485:Protein Binding; D013601:T-Lymphocytes / Q000276:immunology* / Q000378:metabolism
D000199:Actins; D010455:Peptides; D002118:Calcium
T cell activation; T cell receptor; chemical fixation; paraformaldehyde; peptide-MHC complex