Yale researchers report a backup system for IgA antibody production in the gut. The gut immune system encounters many foreign substances from food and microbes, and IgA forms a mucosal barrier that traps and neutralizes pathogens and prevents their attachment to the intestinal lining.
In a study published in Immunity, the team traced B cell responses in mice after immunization. They describe two distinct pathways that produce IgA following immune stimulation. Typically, naïve B cells (IgM) enter germinal centers, acquire mutations for high antigen affinity and class-switch into IgG, IgE or IgA. However, most IgA made in the first three weeks did not derive from germinal centers, while germinal center-derived IgA became detectable in weeks three through six.
Reconstruction of B cell relationships revealed that IgA and IgG frequently shared very close recent ancestors, often IgG1 rather than IgM. This pattern — and the presence of IgG1 in Peyer’s patches, where molecules needed for IgA class-switching are present — is consistent in mice and humans and suggests a sequential switch (IgM → IgG → IgA). The authors say the redundancy in gut immunity ensures IgA production. Future work will investigate why non-germinal center cells acquire mutations. Better understanding of these routes could help design improved mucosal vaccines against intestinal pathogens such as norovirus and rotavirus, and respiratory pathogens such as influenza and SARS‑CoV‑2.
Support for the work came from the National Institutes of Health, Yale University and several research fellowships and centers. Source: Yale.
Difficult words
- mucosal — relating to the moist lining of body organs
- germinal center — area in lymph tissue where B cells maturegerminal centers
- class-switch — change of antibody type produced by B cellsclass-switching
- naïve — not yet exposed to an antigen or infection
- affinity — strength of binding between antibody and antigen
- redundancy — extra systems that ensure a function continues
- sequential — happening in a specific, repeated order
- immunization — process of producing immunity through vaccination
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Discussion questions
- How could understanding the two IgA production pathways help researchers design better mucosal vaccines? Give reasons.
- Why might a sequential switch from IgM to IgG to IgA be beneficial for immune responses in the gut?
- What research methods or experiments would you suggest to investigate why non-germinal center cells acquire mutations?
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