Positive and Negative Selection of Developing Antigen Specific B Cells in a Gut Associated Lymphoid Organ, the Bursa of Fabricius
Year: 2013
Type: dissertation
Abstract: Surface immunoglobulin (sIg) expression is a critical checkpoint in the early stages of B cell development. However it remains controversial as to whether sIg ligation plays a role in gut associated lymphoid tissues such as the bursa of Fabricius in chickens. To assess the role of antigen in B cell development, we constructed sIg related B cell receptors (BCRs) of defined specificity. Initial attempts to generate such BCRs by reverse engineering selected scFv expressing phage derived sequences into intact sIgM revealed a failure to maintain specificity due to loss of antigen binding or heavy chain:light chain pairing incompatibility in the full length immunoglobulin. In contrast, fusion of lamprey variable lymphocyte receptors (VLRs) of defined specificity, such as Phycoerythrin binding VLR, to the chicken sIgM constant region resulted in chimeric antigen specific BCRs that were expressed and supported the early stages of chicken B lymphopoiesis. While VLRPETexpressing B cells specific for Phycoerythrin (PE) passed the sIg selection checkpoint and were detected in the bursa and the periphery, VLRHELTcells specific for the self-antigen Hen Egg Lysozyme (HEL) were not detected. Moreover, i.v. injection of PE into VLRPET expressing chicks during embryogenesis induced deletion of splenic VLRPET B cells. Furthermore, we demonstrated signaling dependent deletion of mCD8:chIg expressing B cells as a consequence of co-expressing TL, a natural ligand of mCD8. While VLRPET expressing B cells disappeared within the first 10 days after hatch in normal chicks, intrabursal application of PE sustained bursal and peripheral VLRPET B cells. Migration of VLRPET expressing B cells to the periphery was enhanced by intrabursal PE and included both short-lived and longer-lived peripheral B cells. This work represents the first evidence for positive and negative selection of B cells in avian gut associated B cell development. It demonstrates distinct B cell fates depending on the route of antigen administration and the requirement for BCR ligation to prolong the survival of bursal and peripheral B cells.
Source: TSpace (University of Toronto)
Author: Dariush Davani
Language: English
Topic: T-cell and B-cell Immunology
Subfield: Immunology
Field: Immunology and Microbiology
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W2725051952