Characterization of hemocyte dynamics in the ovary of Drosophila melanogaster
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Citation
Abstract
The clearance of dead cells and cellular debris is critical for the prevention and regulation of inflammation. Defects in cell clearance, known as phagocytosis, can result in the development of chronic inflammation. Phagocytes, the cells responsible for cell clearance, are typically categorized as professional or nonprofessional phagocytes and most tissue types contain both of these cells. However, some tissues are regarded as “immune-privileged,” meaning that they lack either immune surveillance by traditional immune cells or interact with the immune system in an atypical way. While both professional and nonprofessional phagocytes have been studied individually, their interactions and roles in immune-privileged organs are not yet well-understood. The study of professional phagocytes, often immune cells, in regulating cell clearance and preventing inflammation in immune-privileged organs, as well as how they are barred from entering these organs directly, is important due to the sensitivity of these organs to their environment and the terrible consequences that can arise from disruption of homeostasis. The Drosophila melanogaster ovary is a genetically malleable in vivo model system to study professional phagocyte interactions with an immune-privileged organ. The ovary contains nonprofessional phagocytes that engulf the germline when apoptosis is induced. Clearance of the germline by the nonprofessional epithelial follicle cells has been studied in some detail, however, the fate of these follicle cells once they become obsolete has not been studied. Hemocytes, professional phagocytes analogous to vertebrate macrophages, have been reported to surround the Drosophila ovary, but their interaction with the ovary has not been investigated. The research in this dissertation focuses on the role of hemocytes in maintaining homeostasis of the ovary as well as determining how hemocytes are barred entry from the ovary. The results of this study demonstrate that hemocytes are involved in the clearance of follicle cells in the oviduct and that hemocyte recruitment depends on expression of the cytokine Unpaired3 by the follicle cells of dying egg chambers. This research also demonstrates that hemocyte infiltration is prevented by septate junctions in the epithelial sheath, which protect the developing egg chambers from the surrounding environment. Additionally, disruption of homeostasis via impaired phagocytosis of the germline was found to result in hemocyte infiltration through the epithelial sheath. These findings demonstrate how professional phagocytes can interact with nonprofessional phagocytes and immune-privileged organs, providing new insight into the regulation of immunity.
Description
2024
License
Attribution 4.0 International