Swine GM-CSF (Granulocyte–Macrophage Colony-Stimulating Factor, CSF2) is a hematopoietic cytokine belonging to the colony-stimulating factor family, which also includes G-CSF (CSF3) and M-CSF (CSF1) that regulate the development, proliferation, and activation of myeloid immune cells. In pigs (Sus scrofa), GM-CSF is produced by activated T lymphocytes, macrophages, endothelial cells, fibroblasts, and epithelial cells in response to infection, inflammatory cytokines, or immune stimulation. Swine GM-CSF binds to the GM-CSF receptor (CSF2R) expressed on hematopoietic progenitor cells and mature myeloid cells, activating intracellular signaling pathways such as JAK/STAT, MAPK/ERK, and PI3K–AKT, which promote the proliferation and differentiation of granulocytes, macrophages, and dendritic cells, while enhancing their phagocytic activity and antigen-presenting capacity. In swine immunity, GM-CSF contributes to regulation of innate and adaptive immune responses, particularly during viral and bacterial infections affecting the respiratory and gastrointestinal systems. Pigs are widely used as translational animal models for human infectious disease and vaccine research, and GM-CSF–mediated immune responses have been studied in porcine models of influenza infection, where activation of macrophages and dendritic cells helps coordinate antiviral immunity and inflammatory responses, providing insights relevant to both swine health and human respiratory disease research.