Browsing by Author "Moore, Dannielle Keagen"
Now showing 1 - 1 of 1
Results Per Page
Sort Options
- ItemInvestigation of regulatory B-cell responses during Mycobacterium tuberculosis exposure(Stellenbosch : Stellenbosch University, 2019-03) Moore, Dannielle Keagen; Loxton, Andre G.; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Biomedical Sciences: Molecular Biology and Human Genetics.ENGLISH ABSTRACT: Tuberculosis (TB) remains a global health challenge due to limited understanding of the complex host immune responses required for the successful control and eradication of invading Mycobacterium tuberculosis (M.tb) bacilli. To date, T-cells and macrophages have been regarded as the principle immune cells responsibly for protective anti-TB immunity. However, emerging evidence has revealed a fundamental role of B-lymphocytes (B-cells) during M.tb infection; although the function of B-cells in TB disease incidence and progression remains ill-defined. We hypothesize that B-cells influence anti-TB immune responses through modulation of T-cell activation, and that the microenvironment in which these interactions occur greatly impacts immune cell function, with an emphasis on B-cells. Healthy participants that were either pre-exposed or unexposed to M.tb were recruited for the study. Within the pilot study investigating the effect of B-cells on T-cell function: peripheral blood was collected, and B- or T-cell enriched using magnetic-activated cell sorting (MACS) bead technology for downstream analysis. Following sample collection, autologous T-cells were co-cultured with H37Rv/BCG-stimulated B-cells, pulsed with or without cluster of differentiation 40 Ligand (CD40L) and interleukin-5 (IL5). The resulting B- and T-cell phenotypic frequencies and cytokine profiles were subsequently evaluated. To determine the effect of the microenvironment complexity on cell function, peripheral blood was collected, and B-cell frequency and function (immunoglobulin isotype profile) determined in whole blood, peripheral blood mononuclear cells (PBMCs) and untouched, isolated Bcells following 24-hour stimulation with toll-like receptor 9 agonist (TLR9a) or H37Rv. Our results demonstrate that B-cells are able to modulate T-cell activation and function. We found that Bacillus Calmette-Guérin (BCG) and H37RV alike are able to induce killer/regulatory B-cell phenotypes in QuantiFERON positive and negative participants. Furthermore, the microenvironment was found to have a substantial effect on B-cell function with noticeable changes in B-cell development, shown by a decrease in mature B-cell frequencies following cellular isolation. Likewise, impairment of humoral responses, indicated by hampered ability to produce certain immunoglobulin isotypes in response to antigenic stimulation, were observed for isolated B-cells. Collectively, these findings indicate the potential influence B-cells have in anti-TB immune responses through modulation of T-cell behaviour, underscoring the role B-cells may play in initiating and guiding the immune response against M.tb. Our study highlights the need to further study B-cells as therapeutic targets in novel TB prevention strategies. Additionally, our study identifies significant limitations associated with the use of cell isolation studies for inference of cell function during health and disease. Findings from these studies, while informative, should be interpreted carefully, as the in vitro microenvironment may have considerably influenced the observed results.