Guinea Pig Macrophage Colony-Stimulating Factor (M-CSF) is a cytokine that regulates the development, proliferation, and survival of monocytes and macrophages in guinea pigs (Cavia porcellus). M-CSF is produced by several cell types, including fibroblasts, endothelial cells, epithelial cells, and stromal cells, in response to tissue signals and inflammatory stimuli. Guinea pig M-CSF binds to the colony-stimulating factor-1 receptor (CSF1R), a receptor tyrosine kinase expressed on monocytes and macrophage lineage cells, activating intracellular signaling pathways such as PI3K–AKT, ERK/MAPK, and JAK–STAT that promote differentiation and maintenance of macrophage populations. Through these mechanisms, M-CSF supports macrophage-mediated immune surveillance, phagocytosis, tissue homeostasis, and inflammatory responses. Because macrophages play a key role in host defense, M-CSF–mediated macrophage function is important for maintaining immune health and resistance to infection in guinea pigs. In cell culture, recombinant guinea pig M-CSF is commonly used to promote differentiation of guinea pig monocytes into macrophages and to support macrophage proliferation and functional assays in vitro. Guinea pig M-CSF is also studied in animal model research, particularly in guinea pig models of infectious diseases such as tuberculosis, where macrophage responses are critical for understanding host–pathogen interactions and immune defense mechanisms.