Acute-phase response factor is a transcription factor that binds to the IL-6-responsive elements identified in the promoters of various acute-phase protein genes. This protein is activated through phosphorylation in response to various cytokines and growth factors including IFNs, EGF, IL5, IL6, HGF, LIF and BMP2. Once phosphorylated, the protein is translocated into the nucleus. It forms a homodimer or a heterodimer with a related family member (STAT1). It is expressed in heart, brain, placenta, lung, liver, skeletal muscle, kidney and pancreas. Defects in Acute-phase response factor are the cause of hyperimmunoglobulin E recurrent infection syndrome autosomal dominant (AD-HIES). This disorder is characterised by immunodeficiency, chronic eczema, recurrent Staphylococcal infections, increased serum IgE, eosinophilia, distinctive coarse facial appearance, abnormal dentition, hyperextensibility of the joints, and bone fractures.