Browsing by Subject "CD4+ T cell"

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    The function of skin resident dendritic cells in CD4+ T cell differentiation
    (2016-08) Yao, Chen
    Skin-resident dendritic cells (DC) play a crucial role in initiation of adaptive immune responses against cutaneous pathogens as well as in the maintenance of peripheral tolerance. However, the immune response induced by skin DC against foreign antigen in the absence of adjuvants has not been addressed. Here we report that, using anti-huLangerin/ muLangerin antibodies, we could specifically target antigens to LC or CD103+ dermal DC. Targeting foreign peptide 2W1S by either LC or CD103+ dDC was sufficient for expansion of naïve CD4+ T cells and induction of T follicular helper cell (Tfh) differentiation. The expansion of Tfh specific to foreign peptide was accompanied by activation and expansion of antigen-specific B cells and the development of a robust antibody response that provided systemic protection against influenza infection. Using huLang LCΔMHC-II mice, we showed that CD4+ T cell proliferation was intact despite the MHC II deficiency on LC after targeting antigen to LC. We found that antigen targeted LC handed over antigen to CD11b+ dDC and DN dDC. We also showed MHC II deficient LC acquired MHC II in the lymph node through cross-dressing. This study reveals a major unappreciated function of skin DC in humoral response, and the communication between DC subsets, which provides insight into DC-targeted vaccine design.
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    The role of T cell receptor affinity in CD4+ T cell differentiation
    (2019-02) Kotov, Dmitri
    Naïve helper T cells become activated when their T cell receptor (TCR) recognizes a microbial peptide presented on MHCII (p:MHCII) by dendritic cells (DCs). During this interaction, DCs provide polarizing cues to guide T cell differentiation towards specific fates, like T follicular helper cells which help B cells. The affinity of TCR for its cognate p:MHCII is known to influence the fate adopted by CD4+ T cells, but the mechanisms responsible for this effect are not completely understood. The mechanism could be T cell extrinsic, by affecting the DC subset a T cell contacts thereby influencing the polarizing factors received, or T cell intrinsic, by modulating TCR signal strength thus regulating genes involved in T cell differentiation. The T cell extrinsic hypothesis was tested with a quantitative, imaging approach called histo-cytometry to analyze the T cell-DC interactions. This technique involves time-consuming manual image analysis. Therefore, we wrote software to automate histo-cytometry analysis, reducing hands-on analysis time by up to 90%. With histo-cytometry, we determined that TCR affinity did not affect the DC subset contacted by CD4+ T cells, rendering the cell extrinsic hypothesis unlikely. We therefore focused on the T cell intrinsic hypothesis by performing a CRISPR/Cas9 screen to identify TCR regulated genes that influence T cell differentiation. This screen revealed two novel regulators of helper T cell differentiation, Eef1e1 and Gbp2, which are expressed at a higher level in high affinity than low affinity T cells. These results suggest that TCR affinity influences helper T cell differentiation intrinsically by regulating genes that control the differentiation process. We next explored the relationship between CD4+ T cell differentiation and cytotoxic activity. This study determined that cytotoxic function of helper T cells was dependent on the Fas pathway and Fas was upregulated on target cells proportional to the TCR affinity of the responding T cells. Additionally, we identified that many different helper T cell subsets express FasL and have cytotoxic potential. Thus, my work could benefit future vaccines by providing greater understanding of how helper T cell fate decisions occur and how these decisions influence cytotoxic function.