Functional strain analysis of the gut microbiota in individuals with IgA deficiency

Immunoglobulin A (IgA) is the main immunoglobulin secreted at mucosal surfaces where it binds microbial antigens in the gut lumen. Despite being ubiquitous at mucosal surfaces, IgA deficiency (IgAD) is mostly asymptomatic or result only in mild clinical manifestations. Here we used a novel species-based functionality approach to investigate the role of IgA in the gut. We show that individuals with IgAD are enriched for species which have an increased inflammatory potential as compared to their household controls. Further we used strain-level analysis to show that the increased level of pathogenic potential is not due to strain selection, suggesting that IgA exerts its function by keeping potentially invading bacteria at bay.