Abstract
The development and diversification of B cells within the avian immune system is a complex system, that is essential in the protection against infection and disease. This process is comprised of three mechanisms: V(D)J gene rearrangement, gene conversion and somatic hypermutation. This thesis aimed to develop a deeper understanding of the impact of these diversification methods on the genetic diversity of the resulting immunoglobulin repertoire, with a particular focus on somatic gene conversion. Investigations into the mechanism of gene conversion highlighted its repetitive and biased nature, which in young birds results in the generation of a B cell immunoglobulin repertoire that is limited in genetic diversity when compared to that which is found in humans. The examination of B cells within the bursa of Fabricius at the single cell level found a heterogenous population of B cells at varying stages of differentiation, highlighting the potential for the bursa of Fabricius to enable terminal differentiation of avian B cells through antigen-induced diversification. Investigation of the genetic repertoire of B cells resulted in the discovery of allelic variants of IgY in several breeds of domestic chicken. Further examination of these variants discovered structural differences between variants with the potential to alter the conformation of the Fc antibody region. The data presented in this thesis contributes to the knowledge of the underlying diversification of avian B cell repertoire, as well as providing key insights for the development of avian vaccines and the development of IgY technology.