A peptide binding weakly to the major histocompatibility molecule augments T cell responses.
An I-A(d)-derived peptide PB1 was found to enhance the reactivity of I-A(d)-restricted T cells. The augmentative effect was not due to the cross-reactivity of PB1 peptide with antigens. PB1 had no effect on T cells specific for I-A(b) and I-E(k), nor did PB1 increase the T cell responses to concanavalin A and staphylococcal enterotoxin B. The strict I-A(d) specificity suggests that PB1 enhances the recognition of antigen-I-A(d) complex by T cell receptor. PB1 bound to I-A(d) weakly. The augmentative effect could be found on other I-A(d)-binding peptides in appropriate conditions; however, PB1 was distinct in its prominently augmentative effect on all the I-A(d)-restricted T cells analyzed. A similar enhancing activity was demonstrated on a synthetic transferrin receptor peptide with minimum affinity for I-A(d). The unusual enhancing activity of PB1 may thus be attributed to the low I-A(d) binding affinity. It was postulated that the binding of low-affinity PB1 would not only stabilize I-A(d) structure, but also enhance the binding of other peptides. This was supported by the increased binding of OVA 323-339 and cI 84-98 to I-A(d) in the presence of PB1. The inclusion of PB1 in the immunization mixture also enhanced T cell responses in vivo, suggesting the possibility of using low-affinity peptide to promote specific immunity.
Feng
M H
MH
Graduate Institute of Microbiology and Immunology, National Yang-Ming Medical School, Tapei, Taiwan, R.O.C.
Lai
M Z
MZ
D000595:Amino Acid Sequence; D000818:Animals; D000941:Antigens / Q000737:chemistry / Q000276:immunology*; D002460:Cell Line; D000949:Histocompatibility Antigens Class II / Q000737:chemistry / Q000276:immunology*; D066298:In Vitro Techniques; D051379:Mice; D008969:Molecular Sequence Data; D010455:Peptides / Q000276:immunology*; D011485:Protein Binding; D013601:T-Lymphocytes / Q000276:immunology*
D000941:Antigens; D000949:Histocompatibility Antigens Class II; C024138:I-E-antigen; D010455:Peptides