part_of part of part of extracellular space immunoglobulin complex immunoglobulin complex, circulating cellular_component antibody Wikipedia:Antibody Note that an immunoglobulin complex has the function of antigen binding if a suitable antigen is available. GO:0042571 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.