Researchers examined how the gut produces immunoglobulin A (IgA), the antibody that forms a mucosal barrier in the intestine. They traced B cell responses in mice after immunization to see which cellular routes make IgA.
Normally, naïve B cells (IgM) enter germinal centers, where they mature, mutate and class-switch once into IgG, IgE or IgA. The team found that most IgA present in the first three weeks after immunization did not come from germinal centers. Germinal center-derived IgA became detectable between weeks three and six.
Unexpectedly, non-germinal center IgA and germinal center IgA had similar antigen specificity and similar numbers of mutations. The researchers also reconstructed evolutionary relationships and saw that IgA and IgG often shared close recent ancestors, suggesting a sequential switch from IgM to IgG and then to IgA. The pattern appeared in both mice and humans, and the finding suggests redundancy in gut immunity and possible implications for mucosal vaccine design.
Difficult words
- immunoglobulin — protein antibody that defends the bodyimmunoglobulin A
- mucosal — related to the moist lining inside the body
- germinal center — area in lymph tissue where B cells maturegerminal centers, germinal center IgA
- naive — not yet activated or experienced immune cellnaïve
- class-switch — process that changes an antibody's class type
- antigen — substance that triggers an immune response
- redundancy — extra or duplicate protection in a biological system
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Discussion questions
- Why could redundancy in gut immunity be useful for protecting the body? Give one or two reasons.
- Why is it important that the same pattern appeared in both mice and humans?
- How might the finding about different cellular routes for IgA influence mucosal vaccine design?
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