Human Fc receptors (Fc gamma R) are membrane glycoproteins that are expressed on all immunologically active cells and have a well-defined role in regulating innate and adaptive immune responses by binding to the immunoglobulin G (IgG) antibody. Among the several classes of Fc receptors, Fc gamma RIIa is the most widely expressed, and it serves as an important reagent in antibody engineering. Here, we report on high cell density cultivations (HCDC) of Escherichia coli for preparative scale production of Fc gamma RIIa in a 6.6 L bioreactor. Briefly, a pH-stat feeding strategy was employed, and two different cell densities (OD(600) of 46 and 100) were examined for the induction of Fc gamma RIIa gene expression. When cells were induced at a high cell density (OD(600) of 100), the cell density increased to an OD(600) of 234 within 9 h after induction, and a 2-fold higher production yield was obtained compared with that of induction at low cell density (OD(600) of 46). After simple purification steps including denaturation and refolding, 87.7 mg of soluble Fc gamma RIIa that was more than 95% pure was obtained from a 20-mL culture with high recovery yield (approximate to 54%). The biological activity of purified Fc gamma RIIa was also confirmed by evaluating its interaction with all subclasses of IgG antibodies using an ELISA bioassay. (C) 2011 Elsevier Inc. All rights reserved.