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Characterisation of the T-cell Component of the Lymph Node Microenvironment in Chronic Lymphocytic Leukaemia

Student thesis: Doctoral ThesisDoctor of Philosophy

The aim of this thesis was to characterise the T-cell component of the lymph node (LN) microenvironment in chronic lymphocytic leukaemia (CLL). It is well established that the proliferation of the neoplastic clone in CLL occurs primarily within the secondary lymphoid tissues and that within LNs these cells are in close contact with T-cells and other elements of the microenvironment. First I present a phenotypic study of the T-cells of the CLL LN obtained by fine needle aspiration. I found that, compared to CLL peripheral blood (PB), CLL LNs contain an excess of effector memory CD4+ T-cells and that the LN T-cells express more PD-1 than those from the PB; suggesting ongoing activation. Multiparameter immunofluorescence microscopy on LN biopsy sections showed that proliferating Ki67+ CLL cells are in contact with CD4+ PD-1+ T-cells. Next I sought to characterise the T-cell receptor (TCR) repertoire of flow sorted LN and PB CD4+ T-cells by spectratyping. This revealed oligoclonality in both compartments, with a significant reduction in TCR diversity in the PD-1hi subset. All subsets were skewed compared to healthy age matched PB. The spectratype profiles were distinct between the LN and PB and therefore likely a result of interaction with different antigens. This data was complemented by high throughput sequencing of the TCR, which showed more sequence overlap between 2 LNs taken from the same CLL patient, than between the LN and PB. Finally I present a preliminary in-vitro study aimed at recapitulating the events in CLL LNs. This study showed that PD-L1 can be upregulated on PB CLL cells by CD3/CD28 stimulation of accompanying T-cells, and that blocking PD-1 can lead to increased secretion of interferon gamma. Taken together these findings suggest that CLL CD4+ T-cells are subject to chronic activation and have undergone antigen driven oligoclonal expansion within the LN.
Original languageEnglish
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Award date2016

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