Human CD4+ memory phenotype T cells use mitochondrial metabolism to generate sensitive IFN-γ responses

The transition of naive T lymphocytes into antigenically activated effector cells is associated with a metabolic shift from oxidative phosphorylation to aerobic glycolysis. This shift facilitates production of the key anti-tumor cytokine interferon (IFN)-γ; however, an associated loss of mitochondrial efficiency in effector T cells ultimately limits anti-tumor immunity. Memory phenotype (MP) T cells are a newly recognized subset that arises through homeostatic activation signals following hematopoietic transplantation. We show here that human CD4+ MP cell differentiation is associated with increased glycolytic and oxidative metabolic activity, but MP cells retain less compromised mitochondria compared to effector CD4+ T cells, and their IFN-γ response is less dependent on glucose and more reliant on glutamine. MP cells also produced IFN-γ more efficiently in response to weak T cell receptor (TCR) agonism than effectors and mediated stronger responses to transformed B cells. MP cells may thus be particularly well suited to carry out sustained immunosurveillance against neoplastic cells.

Transcription factor EGR2 controls homing and pathogenicity of TH17 cells in the central nervous system

CD4+ T helper 17 (TH17) cells protect barrier tissues but also trigger autoimmunity. The mechanisms behind these opposing processes remain unclear. Here, we found that the transcription factor EGR2 controlled the transcriptional program of pathogenic TH17 cells in the central nervous system (CNS) but not that of protective TH17 cells at barrier sites. EGR2 was significantly elevated in myelin-reactive CD4+ T cells from patients with multiple sclerosis and mice with autoimmune neuroinflammation. The EGR2 transcriptional program was intricately woven within the TH17 cell transcriptional regulatory network and showed high interconnectivity with core TH17 cell-specific transcription factors. Mechanistically, EGR2 enhanced TH17 cell differentiation and myeloid cell recruitment to the CNS by upregulating pathogenesis-associated genes and myelomonocytic chemokines. T cell-specific deletion of Egr2 attenuated neuroinflammation without compromising the host's ability to control infections. Our study shows that EGR2 regulates tissue-specific and disease-specific functions in pathogenic TH17 cells in the CNS.

Recognition of an MHC Class I-Restricted Antigenic Peptide Can Be Modulated by para-Substitution of Its Buried Tyrosine Residues in a TCR-Specific Manner

Conformational dependence of TCR contact residues of the H-2Kb molecule on the two buried tyrosine side chains of the vesicular stomatitis virus (VSV)-8 peptide was investigated by systematic substitutions of the tyrosines with phenylalanine, p-fluorophenylalanine (pFF), or p-bromophenylalanine (pBrF). The results of peptide competition CTL assays revealed that all of the peptide variants, except for the pBrF analogues, had near-native binding to the H-2Kb molecule. Epitope-mapped anti-H-2Kb mAbs detected conformational differences among H-2Kb molecules stabilized with these VSV-8 variants on RMA-S cells. Selective recognition of the VSV-8 analogues was displayed by a panel of three H-2Kb-restricted, anti-VSV-8 TCRs. Thus, these substitutions result in an antigenically significant conformational change of the MHC molecular surface structure at both C and D pockets, and the effect of this change on cognate T cell recognition is dependent on the TCR structure. Our results confirm that the structure of buried peptide side chains can determine the surface conformation of the MHC molecule and demonstrate that even a very subtle structural nuance of the buried side chain can be incorporated into the surface conformation of the MHC molecule. The ability of buried residues to modulate this molecular surface augments the number of residues on the MHC-peptide complex that can be recognized as “foreign” by the CD8+ T cell repertoire and allows for a higher level of antigenic discrimination. This may be an important mechanism to expand the total number of TCR specificities that can respond to a single peptide determinant.