Orosomucoid 1, also known as ORM1, is an acute phase plasma protein synthesized by the liver. The protein is believed to regulate the interaction between blood cells and endothelial cells, and together with haptoglobin and C reactive protein, also regulates the extravasation of the cells during infection and inflammation. Expression of ORM1 is induced by acute-phase stimulatory agents such as bacterial lipopolysaccharides.