ISG15 is a ubiquitin like protein that binds to intracellular target proteins after activation by interferon - α (IFNA) and - β (IFNB). ISG15 exhibits specific chemotactic activity towards neutrophils and activates them to induce the release of eosinophil chemokines. It can act as a trans acting binding factor to guide the binding of the target protein to the intermediate filament. It may also participate in autocrine, paracrine, and endocrine mechanisms, such as intercellular signaling, possibly partially by inducing monocytes and macrophages to secrete IFN - γ. It appears to exhibit antiviral activity during viral infection.
