Sequencing the Immunoglobulin Heavy-Chain Locus (IgH) in Turquoise Killifish (Nothobranchius furzeri).

B cells undergo a process of somatic recombination leading to the synthesis of a staggering diversity of transmembrane and secreted antibodies. This process dates back to the evolution of jawed vertebrates and is pivotal to the origin of lymphocyte-based adaptive immune responses. Here, we optimized a sequencing-based protocol to characterize B-cell-specific IgH transcripts from bulk RNA in the African turquoise killifish, an emerging model organism characterized by naturally short life span and by a vast range of age-dependent dysfunctions.

Extensive age-dependent loss of antibody diversity in naturally short-lived turquoise killifish.

Aging individuals exhibit a pervasive decline in adaptive immune function, with important implications for health and lifespan. Previous studies have found a pervasive loss of immune-repertoire diversity in human peripheral blood during aging; however, little is known about repertoire aging in other immune compartments, or in species other than humans. Here, we perform the first study of immune-repertoire aging in an emerging model of vertebrate aging, the African turquoise killifish (Nothobranchius furzeri). Despite their extremely short lifespans, these killifish exhibit complex and individualized heavy-chain repertoires, with a generative process capable of producing millions of distinct productive sequences. Whole-body killifish repertoires decline rapidly in within-individual diversity with age, while between-individual variability increases. Large, expanded B-cell clones exhibit far greater diversity loss with age than small clones, suggesting important differences in how age affects different B-cell populations. The immune repertoires of isolated intestinal samples exhibit especially dramatic age-related diversity loss, related to an elevated prevalence of expanded clones. Lower intestinal repertoire diversity was also associated with transcriptomic signatures of reduced B-cell activity, supporting a functional role for diversity changes in killifish immunosenescence. Our results highlight important differences in systemic vs. organ-specific aging dynamics in the adaptive immune system.