Immunoglobulin J chain, also known as IGJ, serves to link two monomer units of either IgM or IgA. In the case of IgM, the J chain-joined dimer is a nucleating unit for the IgM pentamer, and in the case of IgA it induces larger polymers. It also helps to bind these immunoglobulins to secretory component. Recombinant human IGJ protein, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography techniques.