TNFR:Fc consists of two molecules of the extracellular portion of the p75 receptor, each consisting of 235 amino acids. The two receptors are fused to the Fc portion of human IgG1, which consists of 232 amino acids. The gene fragments encoding the truncated TNFR and the Fc portion of human IgG1 are expressed in a Chinese hamster ovary cell line.