Infliximab is a chimeric IgG1 monoclonal antibody with an approximate molecular weight of 149,100 Dalton. It is composed of human constant and murine variable regions. Infliximab binds specifically to human tumour necrosis factor alpha (TNF-a) with an association constant of 1010 M-1. Infliximab is produced by a recombinant cell line cultured by continuous perfusion and is purified by a series of steps that includes measures to inactivate and remove viruses.