Work Package 3
Towards a better understanding of the antibody response in chickens by characterizing germinal center and antigen-specific B cells
The chicken B cell system differs substantially from that in human and mice. While mammalian B cell development takes place in the bone marrow, avian B cells develop in the bursa of Fabricius. and, whereas human and mouse B cell receptor (BCR) diversity is initially obtained by gene rearrangement, chicken BCRs are diversified by gene conversion. Furthermore, there are also marked differences in peripheral B cell differentiation. In order to generate a protective antibody response, B cells must differentiate into plasma cells (PCs) and produce high amounts of antibodies with varying life spans, isotypes and binding specificities. In mammals, these processes can happen in a short-lived reaction in the B cell areas of secondary lymphoid structures or in the context of a longer process in a germinal center (GC), where immunoglobulin class switch, selection of antibodies with increased affinity, and differentiation of long-lived PCs and memory B cells (MBCs) take place. Although chickens are the most vaccinated livestock species and many vaccines provide protection via antibodies, there are significant gaps in our understanding of the spatial, temporal, mechanistic, and qualitative aspects of antibody formation in chickens. GCs have been identified in all secondary lymphatic organs of the chicken, but they differ significantly in their structure and location from mammalian GCs and limited information is available regarding their cellular composition and function. Therefore, we will isolate GCs and phenotype GC B cells by flow cytometry and single cell sequencing. In addition, BCR sequencing will be performed to resolve the question of GC clonality, BCR modifications and BCR selection. Once the phenotype of GC B cells is established, we aim to differentiate GC B cells in vitro using our established B cell culture system and additional recombinant cytokines, such as IL-21. In addition to immunoglobulin class switching, a hallmark of the antibody response in mammals is the increasing affinity of the antibodies during an immune response. Given the discrepancies in the scientific literature for chickens, we will employ state-of-the-art technology to investigate whether affinity maturation occurs in chickens during the antibody response. Finally, we will analyze both the quality and quantity of antigenspecific B cells. To achieve this, we will use avian influenza as a model and employ recombinant hemagglutinin to target the cells. This highly collaborative work will provide important insights into the mechanisms of the humoral immune response in chickens and provide the basis for the development of more specific and longer-lasting vaccines.
Principal investigator:
PhD-student:
tba