Macrophages are immune cells that play critical roles in fighting disease, healing tissues, and maintaining overall health. Their behavior can shift in ways that either help or harm the body, depending on their environment. Histone lactylation, in which lactate, a small molecule metabolite produced in the body, changes how genes are turned on or off, may help explain how these cells change roles. This project will use synthetic biology to create precision tools that can add or remove lactylation marks on DNA-packaging proteins. These tools will help scientists understand how lactylation affects macrophage behavior and could lead to new ways to control immune responses in diseases like cancer. Course module development and support of undergraduate researchers will help to grow the biomanufacturing workforce. This project investigates the functional role of histone lactylation in macrophage polarization. Lactylation has been linked to macrophage transitions from inflammatory (M1) to anti-inflammatory (M2) phenotypes, particularly within the immunosuppressive tumor microenvironment. The central hypothesis is that modulating histone lactylation can selectively control macrophage phenotype, independent of external stimuli. In Phase I, lactylation writers and erasers will be created. These are enzymes capable of adding or removing lactylation at specific sites on histones. First, a detailed map of histone lactylation across macrophage polarization states and external stimuli wi