Conjoined ontogeny of the B cell receptor repertoire and microbiome in mice

The immune system matures throughout childhood to achieve full functionality in protecting our bodies against threats. The immune system has a strong reciprocal symbiosis with the host bacterial population and the two systems co-develop, shaping each other. Despite their fundamental role in health physiology, the conjoined ontogeny of these systems is poorly characterized. Here, we study the development of B cell repertoire by analysing high throughput sequencing of their receptors in several time points of young mice. In parallel, we explored the development of the gut microbiome. We discovered that gut IgA repertoires change throughout childhood, including an increase in complementary determining region 3 (CDR3) lengths and somatic hypermutation (SHM) levels. This is in contrast to the spleen IgM repertoires that remain stable and distinct from the IgA repertoires in the gut. We also quantified the associations between diversity indices of the B cell repertoires and the micorbiome, as well as correlations between bacterial and B cell receptor clusters. Our results shed light on the conjoined ontogeny of the adaptive immune system and the microbiome, providing a baseline for future research.