M1 macrophages are primarily activated through the interaction with microbial products, such as lipopolysaccharides (LPS), and by cytokines like interferon-gamma (IFN-γ). This activation can be initiated by the binding of these molecules to specific receptors on the surface of the macrophages, leading to a cascade of intracellular signaling events that culminate in the activation of transcription factors such as NF-κB and STAT1.
