The J Chain's molecular weight is approximately 15 kDa. It exhibits a standard immunoglobulin folding structure of two β-pleated sheets of four ribbons folded against one another. It has 8 cystine residues. Two of these residues link the α chains of IgA or the μ chains of IgM via disulfide bridges, effectively serving as the "glue" between two Fc regions of the antibody.
The J-chain shows a large degree of homology between avian and human species, suggesting that it serves an important function.
The J Chain is required for IgM or IgA to be secreted into mucosa.
Because IgM and IgA are the only two types of antibody that polymerize, initial hypotheses stated that J chain was required for polymerization. However, it was subsequently found that IgM is able to polymerize in the absence of J chain as both a pentamer and a hexamer, however, both of these exist to lesser numbers in organisms lacking J chains. In such cases, there are also fewer IgA dimers.
Mole JE, Bhown AS, Bennett JC (1977). "Primary structure of human J chain: alignment of peptides from chemical and enzymatic hydrolyses.". Biochemistry. 16 (16): 3507–13. PMID407930. doi:10.1021/bi00635a002.
Bastian A, Kratzin H, Eckart K, Hilschmann N (1993). "Intra- and interchain disulfide bridges of the human J chain in secretory immunoglobulin A.". Biol. Chem. Hoppe-Seyler. 373 (12): 1255–63. PMID1292512. doi:10.1515/bchm3.1992.373.2.1255.
Frutiger S, Hughes GJ, Paquet N, et al. (1993). "Disulfide bond assignment in human J chain and its covalent pairing with immunoglobulin M.". Biochemistry. 31 (50): 12643–7. PMID1472500. doi:10.1021/bi00165a014.
Moro I, Iwase T, Komiyama K, et al. (1990). "Immunoglobulin A (IgA) polymerization sites in human immunocytes: immunoelectron microscopic study.". Cell Struct. Funct. 15 (2): 85–91. PMID2113434. doi:10.1247/csf.15.85.
Alberini CM, Bet P, Milstein C, Sitia R (1990). "Secretion of immunoglobulin M assembly intermediates in the presence of reducing agents.". Nature. 347 (6292): 485–7. PMID2120591. doi:10.1038/347485a0.
Sumi Y, Nagura H, Kaneda T, Oka T (1989). "Immunoelectron microscopical localization of immunoglobulins, secretory component and J chain in the human minor salivary glands.". J. Oral Pathol. 17 (8): 390–5. PMID3146624. doi:10.1111/j.1600-0714.1988.tb01303.x.
Iwase T, Saito I, Takahashi T, et al. (1994). "Early expression of human J chain and mu chain gene in the fetal liver.". Cell Struct. Funct. 18 (5): 297–302. PMID8168154. doi:10.1247/csf.18.297.
Harper SJ, Pringle JH, Wicks AC, et al. (1994). "Expression of J chain mRNA in duodenal IgA plasma cells in IgA nephropathy.". Kidney Int. 45 (3): 836–44. PMID8196286. doi:10.1038/ki.1994.110.
Bjercke S, Brandtzaeg P (1994). "Glandular distribution of immunoglobulins, J chain, secretory component, and HLA-DR in the human endometrium throughout the menstrual cycle.". Hum. Reprod. 8 (9): 1420–5. PMID8253928.
Bertrand FE, Billips LG, Gartland GL, et al. (1996). "The J chain gene is transcribed during B and T lymphopoiesis in humans.". J. Immunol. 156 (11): 4240–4. PMID8666793.
Atkin JD, Pleass RJ, Owens RJ, Woof JM (1996). "Mutagenesis of the human IgA1 heavy chain tailpiece that prevents dimer assembly.". J. Immunol. 157 (1): 156–9. PMID8683109.