6kxs

Structural highlights

Disease

[IGHM_HUMAN] Autosomal agammaglobulinemia. The disease is caused by mutations affecting the gene represented in this entry.^[1]

Function

[IGHM_HUMAN] IgM antibodies play an important role in primary defense mechanisms. They have been shown to be involved in early recognition of external invaders like bacteria and viruses, cellular waste and modified self, as well as in recognition and elimination of precancerous and cancerous lesions. The membrane-bound form is found in the majority of normal B-cells alongside with IgD. Membrane-bound IgM induces the phosphorylation of CD79A and CD79B by the Src family of protein tyrosine kinases. It may cause death of cells by apoptosis. It is also found in soluble form, which represents about 30% of the total serum immunoglobulins where it is found almost exclusively as a homopentamer. After the antigen binds to the B-cell receptor, the secreted form is secreted in large amounts.^[2] [PIGR_HUMAN] This receptor binds polymeric IgA and IgM at the basolateral surface of epithelial cells. The complex is then transported across the cell to be secreted at the apical surface. During this process a cleavage occurs that separates the extracellular (known as the secretory component) from the transmembrane segment. [IGJ_HUMAN] 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 help to bind these immunoglobulins to secretory component.[UniProtKB:P01592]

References

1. ↑ Yel L, Minegishi Y, Coustan-Smith E, Buckley RH, Trubel H, Pachman LM, Kitchingman GR, Campana D, Rohrer J, Conley ME. Mutations in the mu heavy-chain gene in patients with agammaglobulinemia. N Engl J Med. 1996 Nov 14;335(20):1486-93. PMID:8890099 doi:http://dx.doi.org/10.1056/NEJM199611143352003
2. ↑ Tisch R, Roifman CM, Hozumi N. Functional differences between immunoglobulins M and D expressed on the surface of an immature B-cell line. Proc Natl Acad Sci U S A. 1988 Sep;85(18):6914-8. PMID:3137579