Mouse Interleukin-34 (IL-34) is a cytokine involved in the regulation of innate immune responses and macrophage biology in mice (Mus musculus). IL-34 is produced by a variety of cell types, including epithelial cells, fibroblasts, neurons, and immune cells, in response to inflammatory signals and tissue stress. Mouse IL-34 functions primarily as a ligand for the colony-stimulating factor-1 receptor (CSF1R), activating intracellular signaling pathways such as ERK, JAK–STAT, and PI3K–AKT that promote survival, proliferation, and differentiation of monocytes and macrophages. Through these mechanisms, IL-34 contributes to the development and maintenance of tissue-resident macrophages and microglia and plays a role in regulating inflammatory responses and tissue homeostasis. In mice, IL-34 is particularly important for the maintenance of microglia in the central nervous system and Langerhans cells in the skin. In cell culture, recombinant mouse IL-34 is commonly used to promote differentiation and survival of monocytes into macrophages or microglia-like cells and to support macrophage proliferation and functional studies in in vitro immunology and neuroimmunology assays.