Browsing by Author "Munshi, Khawalah Abid"

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The effect of Granulocyte-Macrophage colony- stimulating factor (GM-CSF) on the immune response against Candida albicans using human inflammatory monocytes.
(Saudi Digital Library, 2026) Munshi, Khawalah Abid; Martinez-Pomares, Luisa
Granulocyte-macrophage colony-stimulating factor (GM-CSF) plays a pivotal role in antimicrobial immunity by enhancing survival, adhesion, and migration of innate immune cells, including neutrophils, macrophages, and monocytes. Monocytes and macrophages are central for host defence against fungal pathogens such as Candida albicans (C. albicans), acting independently or synergistically with neutrophils. C. albicans is an opportunistic fungal pathogen that lives typically as a commensal. Infection with C. albicans occurs when it shifts from innocuous to pathogenic, often leading to mucosal or systemic diseases. This study investigates how GM-CSF modulates the activity of human inflammatory monocytes during C. albicans infection, aiming to uncover protective mechanisms and determine the therapeutic potential of GM-CSF in the context of fungal infection. The work is presented in three results chapters. Chapter 3 centres on the characterisation of monocytes treated with GM-CSF in comparison to M-CSF-treated monocytes, used as negative controls. GM- CSF and M-CSF monocytes display similar viability (~95%), but GM-CSF monocytes had enhanced expression of CD11b, and HLA-DR compared to M- CSF monocytes. This indicates a significant effect of GM-CSF on monocyte activation. In addition, we observed a substantial increased expression of the mannose receptor MR (CD206), Dectin-1 and CLEC5A, all of which are C-type lectin receptors that specialise in carbohydrate recognition and play a crucial role in detecting infections. Levels of Dectin-2 and the production of extracellular vesicles (EVs), were not affected by GM-CSF. Chapter 4 centres on responses of monocytes to infection with C. albicans and how are affected by GM-CSF. We exposed M-CSF and GM-CSF-monocytes to C. albicans at MOI 1 (cytokine secretion, CFU) or MOI 10 (phagocytosis), at 37 °C, 5% CO2, in the presence of human serum for 1 and 3 h. In response to infection with C. albicans, GM-CSF-treated monocytes, compared to M-CSF- treated monocytes, increased TNF-α, IL-6, IL-1β and CCL22 secretion despite similar phagocytic activity and fungal viability (CFU). Interestingly, GM-CSF- monocytes more effectively control hypha growth, indicating enhanced anti- fungal activity and differential phagosome maturation. These results were linked to a drastic reduction of surface MR after C. albicans uptake in GM-CSF monocytes, which would be consistent with enhanced MR shedding. Chapter 5 considers the role of MR in the response of GM-CSF- monocytes to C. albicans. MR surface expression was inhibited using specific sulfated glycopolymers (sGP). sGP treatment reduced MR expression, which resulted in the reduction of TNF-α production during infection, indicating that MR plays an essential role in modulating inflammation during C. albicans infection. Chapter 6 extended the investigation to induced pluripotent stem cell–derived macrophages (iMacs). The expression of CD45 and CD14 confirmed their macrophage identity. Although the study was limited in both replicates and experimental diversity, we were able to show that iMacs treated with GM-CSF expressed MR and Dectin-1, as determined by qPCR analysis (N=3). In contrast, cytokine secretion was not detected in these cells under the conditions tested. We also performed a CFU assay following the same experimental design used with primary monocytes; although conducted only once, the outcome was consistent with the results obtained from primary cells. Overall, ongoing work aims to clarify the mechanisms underlying hyphal growth restriction and MR-mediated responses, thereby improving our understanding of how GM-CSF confers antifungal protection. Further research will be required to elucidate the effector functions of iMacs and to explore their potential as a model system for studying fungal infections.
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