Immunoglobulin A: a bridge between innate and adaptive immunity

Area of Science:

• Immunology
• Microbiology
• Gastroenterology

Background:

• Immunoglobulin A (IgA) is the most abundant antibody in mammals, primarily found at mucosal surfaces.
• Its precise functions in host-microbe interactions and pathogen defense are still being elucidated.
• Understanding IgA is key to comprehending mucosal immunity and the gut microbiome.

Purpose of the Study:

• To review recent advancements in understanding the role of IgA in host-microbe mutualism.
• To summarize IgA's function in protecting against pathogens at mucosal surfaces.
• To highlight experimental evidence supporting IgA's functional importance.

Main Methods:

• Review of recent scientific literature and experimental studies on immunoglobulin A.
• Analysis of findings related to IgA specificity, priming, and mutation.
• Examination of T-cell-dependent and T-cell-independent pathways of IgA induction.

Main Results:

• Intestinal IgA is highly specific to commensal bacteria and induces long-lasting immune priming.
• Somatic hypermutation of IgA enhances affinity to commensals, crucial for mucosal protection.
• IgA can be induced via both T-cell-dependent and T-cell-independent pathways.

Conclusions:

• Mucosal protection via antibody secretion is an ancient evolutionary function.
• Mammalian IgA, through various pathways and affinity maturation, supports host-microbial symbiosis.
• Enhanced IgA affinity via gene mutation significantly improves mucosal defense.