immunoglobulin complex immunoglobulin complex, circulating An immunoglobulin complex that is secreted into extracellular space and found in mucosal areas or other tissues or circulating in the blood or lymph. In its canonical form, a circulating immunoglobulin complex is composed of two identical heavy chains and two identical light chains, held together by disulfide bonds. Some forms of are polymers of the basic structure and contain additional components such as J-chain and the secretory component. GO:0042571 Note that an immunoglobulin complex has the function of antigen binding if a suitable antigen is available. Wikipedia:Antibody antibody cellular_component go.owl obi.owl extracellular region part