Functional and Phenotypic Evidence for Presentation of Eα52–68 Structurally Related Self-Peptide(s) in I-Eα-Deficient Mice

Abstract

The Y-Ae mAb and the 1H3.1 TCR-αβ (Vα1/Vβ6) are two immune receptors specific for I-Ab MHC class II molecules complexed to the 52–68 fragment of the α-chain of I-E class II molecules (the Eα52–68 peptide). A profound intrathymic negative selection occurs in 1H3.1 TCR transgenic mice in the presence of an I-Eα transgene. The administration of mAbs to 1H3.1/I-Eα double-transgenic newborn mice reveals that Y-Ae, but not the isotype-matched anti-I-E Y17 mAb, rescues a significant number of mature (Vβ6highCD4+CD8−) thymocytes and allows the detection of Eα52–68-reactive T cells in the periphery. These observations indicate that deletion of autoreactive T cells can be specifically inhibited in vivo by an mAb specific for the deleting self-peptide:self-MHC class II complex. Similar inhibition experiments indicate that C57BL/6 (I-Ab+/I-Eα−) mice constitutively express an Eα-independent, Y-Ae-recognizable epitope(s). This finding is confirmed by the phenotypic analysis of mature (MHC class II high) C57BL/6 bone marrow-derived dendritic cells. Collectively, these observations further illustrate the peptide specificity of negative selection and demonstrate that MHC class II-positive cells from unmanipulated C57BL/6 mice that lack a functional I-Eα gene can assemble one or more self-peptide:I-Ab complexes recognizable by the Eα52–68:I-Ab complex-specific Y-Ae mAb.

APCs Present Aβk-Derived Peptides That Are Autoantigenic to Type B T Cells

“…In mice expressing E␣, the epitope is expressed in abundance in both spleen and thymus (22). This system has been instrumental in defining the role of self peptide-MHC recognition in both positive and negative selection (23)(24)(25)(26)(27)(28). Two studies in particular by Janeway's group merit discussion in light of the results reported here.…”

Paradoxical intrathymic positive selection in mice with only a covalently presented agonist peptide

“…C57BL͞6 (B6), SJL, B10.BR-H2 k2 H2-T18 a ͞SgSnJ (B10.BR), and B10.A-H2 i5 H2-Tl8 a (5R)SgSnJ (5R) mice were obtained from The Jackson Laboratory. The 1H3.1 TCR Tg mice (V␣1͞V␤6) are described elsewhere (33). The I-A b -Ep mice (20) mAb Treatment of Newborn Mice.…”

“…DCs were generated in vitro from BM progenitors in complete RPMI medium 1640 supplemented with 1% recombinant granulocyte͞macrophage colony-stimulating factor as described (33,35,36). Apoptotic B cells were derived by culturing splenocytes with 10 g͞ml LPS for 5 days in complete media.…”

Increased competition for antigen during priming negatively impacts the generation of memory CD4 T cells

“…To dissociate competition for antigen from other events, we used the Y-Ae mAb specific for MHC class II E␣ peptide complexes (35,36). The Y-Ae mAb blocks antigen presentation in vitro (37-39) and interferes with negative selection in the thymus in transgenic systems (38). Therefore, we tested whether Y-Ae treatment interfered with E␣ presentation to TEa cells during infection.…”