Interferon-gamma Mediated Bacterial Restriction in Macrophages

Mentor: Karolina Maciag

Macrophage cells engulf and kill bacteria, in part through fusion of lysosomal vesicles with bacterial phagosomes. The cytokine IFNγ increases the effectiveness of this process. Some bacteria are able to grow inside macrophages by preventing phagosome maturation. Karen investigated the effects of IFNγ on vesicle trafficking, with the hopes of discovering genes that help overcome the phagosome maturation arrest caused by these bacteria. In Karen’s project, she validated and characterized three top candidates from a previous screen for genes potentially displaying such roles.

Karen and her mentor successfully knocked down all three of these candidate genes by RNAi. She found that all three of these genes were regulated by IFNγ. To support the hypothesis that these three genes may indeed be involved in phagosome maturation, Karen eliminated several alternative hypotheses for the roles of these genes. She showed that these three genes neither influenced the phagocytic uptake of the bacteria, nor increased the density of lysosomes in the macrophages. Karen’s findings support the hypothesis that these genes play roles in vesicle trafficking during the process of phagosome maturation.

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Karen, a senior at Belmont High School, investigated genes involved in phagosome maturation, which is essential for the ability of macrophages to kill bacteria.