Abstract
Recent discoveries have shed new light onto immunoglobulin M (IgM), an ancient antibody class preserved throughout evolution in all vertebrates. First, IgM – long thought to be a perfect pentamer – was shown to be asymmetric, resembling a quasi-hexamer missing one monomer and containing a gap. Second, this gap allows IgM to serve as carrier of a specific host protein, apoptosis inhibitor of macrophages (AIM), which is released to promote removal of dead-cell debris, cancer cells, or pathogens. Third, recombinant IgM delivered mucosally by passive immunization gave proof-of-concept that this antibody class can prevent mucosal simian-human immunodeficiency virus transmission in non-human primates. Finally, IgM’s role in adaptive immunity goes beyond being only a first defender to respond to pathogen invasion, as long-lived IgM plasma cells have been observed predominantly residing in the spleen. In fact, IgM produced by such cells contained somatic hypermutations and was linked to protection against lethal influenza virus challenge in murine models. Importantly, such long-lived IgM plasma cells had been induced by immunization 1 year before challenge. Together, new data on IgM function raise the possibility that vaccine strategies aimed at preventing virus acquisition could include this ancient weapon.
Highlights
IntroductionSpecialty section: This article was submitted to
Specialty section: This article was submitted toViral Immunology, a section of the journal Frontiers in ImmunologyReceived: 09 June 2020 Accepted: 20 July 2020 Published: 11 August 2020Citation: Gong S and Ruprecht RM (2020)Immunoglobulin M: An Ancient Antiviral Weapon – Rediscovered.Front
The joining chain (J chain) allows immunoglobulin M (IgM) to be transported across mucosal epithelia through binding with the polymeric immunoglobulin receptor, an interaction that leads to the formation of secretory IgM [3]
Summary
Specialty section: This article was submitted to. Viral Immunology, a section of the journal Frontiers in Immunology. Received: 09 June 2020 Accepted: 20 July 2020 Published: 11 August 2020. Immunoglobulin M: An Ancient Antiviral Weapon – Rediscovered. Immunoglobulin M (IgM) is the first responder to foreign invaders – including viral pathogens that cause major pandemics. Its monomeric form is expressed on B cells as the B-cell antigen receptor. IgM is predominantly pentameric and contains the joining chain (J chain). IgM is present at a relatively high concentration in serum (∼1.47 mg/ml) [2]. The J chain allows IgM to be transported across mucosal epithelia through binding with the polymeric immunoglobulin receptor (pIgR), an interaction that leads to the formation of secretory IgM [3]
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