ABSTRACT
The T-cell antigen receptor (TCR) complex contains 10 copies of a di-tyrosine Immunoreceptor-Tyrosine-based-Activation-Motif (ITAM) that initiates TCR signalling by recruiting protein tyrosine kinases. ITAM multiplicity amplifies TCR signals, but the importance of this capability for T-cell responses remains undefined. Most TCR ITAMs (6 of 10) are contributed by the CD3ζ subunits. We generated 'knock-in' mice that express non-signalling CD3ζ chains in lieu of wild-type CD3ζ. Here we demonstrate that ITAM multiplicity is important for the development of innate-like T-cells and follicular helper T-cells, events that are known to require strong/sustained TCR-ligand interactions, but is not essential for 'general' T-cell responses including proliferation and cytokine production or for the generation of a diverse antigen-reactive TCR repertoire.
Subject(s)
Immunoreceptor Tyrosine-Based Activation Motif , Receptors, Antigen, T-Cell/chemistry , Receptors, Antigen, T-Cell/metabolism , T-Lymphocytes, Helper-Inducer/cytology , Animals , Antigens/immunology , Cell Proliferation , Clone Cells , Female , Immunologic Memory , Male , Mice, Inbred C57BL , Mice, Transgenic , Natural Killer T-Cells/cytology , Natural Killer T-Cells/immunology , Receptors, Antigen, T-Cell, alpha-beta/chemistry , Receptors, Antigen, T-Cell, alpha-beta/metabolism , Receptors, Antigen, T-Cell, gamma-delta/chemistry , Receptors, Antigen, T-Cell, gamma-delta/metabolism , Signal Transduction , Structure-Activity RelationshipABSTRACT
Mycobacterium bovis BCG is still the most widely used vaccine against tuberculosis and CD8(+) T cells play important roles in fighting infection. We investigated how well antigen is processed and presented to CD8(+) T cells using the same well-characterized CD8(+) T cell epitope SIINFEKL expressed in either a cytoplasmic (GFP-OVA) or secreted (85B-OVA) context from BCG. We report that secreted SIINFEKL from 85B-OVA BCG is presented better than cytoplasmic SIINFEKL expressed by GFP-OVA BCG.
Subject(s)
CD8-Positive T-Lymphocytes/immunology , Epitopes, T-Lymphocyte/metabolism , Ovalbumin/metabolism , Animals , BCG Vaccine/immunology , Cytoplasm/drug effects , Flow Cytometry , Lymphocyte Activation , Mice , Mice, Inbred C57BL , Peptide Fragments/metabolism , Recombinant Proteins/genetics , Recombinant Proteins/metabolism , Spleen/cytologyABSTRACT
Neuroinflammation often starts with the invasion of T lymphocytes into the CNS leading to recruitment of macrophages and amplification of inflammation. In this study, we show that dendritic cells (DCs) facilitate T-T cell help in the CNS and contribute to the amplification of local neuroinflammation. We adoptively transferred defined amounts of naive TCR-transgenic (TCR) recombination-activating gene-1-deficient T cells into another TCR-transgenic mouse strain expressing different Ag specificity. Following adoptive transfers, we coinjected DCs that presented one or multiple Ags into the brain and followed the activation of T cells with defined specificities simultaneously. Injection of DCs presenting both Ags simultaneously led to significantly higher infiltration of T cells into the brain compared with injection of a mixture of DCs pulsed with two Ags separately. DCs mediated either cooperative or competitive interactions between T cell populations with different specificities depending upon their MHC-restricting element usage. These results suggest that DC-mediated cooperation between brain-infiltrating T cells of different Ag specificities in the CNS plays an important role in regulation of neuroinflammation. This work also implies that blocking Ag-specific responses may block not only the targeted specificities, but may also effectively block their cooperative assistance to other T cells. Therefore, these data justify more attention to Ag-specific therapeutic approaches for neuroinflammation.
