Defense Date

2012

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Microbiology & Immunology

First Advisor

Daniel H Conrad

Abstract

In these studies we sought to determine the role of Fyn kinase and ADAM10 in B cell biology. A disintegrin and metalloproteinase 10 (ADAM10) is a zinc dependent proteinase related to matrix metalloproteinases. ADAM10 has emerged as a key regulator of cellular processes by cleaving and shedding extracellular domains of multiple transmembrane receptors and ligands. In particular, ADAM10 has been identified as a key regulator of lymphocyte development. Here we report that ADAM10 is dispensable for early B cell development within the bone marrow. However, deletion of ADAM10 from all peripheral B cells or in post-switch cells leads to severe impairments in humoral responses. When ADAM10 was deleted from all peripheral B cells a decrease in antigen specific IgG production was seen both with respect to serum levels and IgG ASCs, indicating that plasma cell (PC) differentiation is influenced. Cells producing high affinity antigen specific antibodies were particularly affected, consistent with defects in germinal center (GC) reactions. Moreover, changes in lymphoid architecture were also observed. Consistent with these findings, follicular dendritic cell (FDC)-reticula was undetectable following immunization. On the other hand, when ADAM10 was deleted in post-switch B cells, GC formation and lymphoid architecture were not impaired. Despite normal architecture, however, antibody production was still affected, likely due to abnormal gene expression in ADAM10-deficient PCs. Consistent with this hypothesis, PCs isolated from ADAM10Δ/ΔIgG1-cre+/- showed decreased expression of genes that facilitate plasma cell differentiation and function and increased expression of Bcl6, an inhibitor of PC differentiation. Fyn kinase is a member of the Src protein tyrosine kinase. Fyn is widely expressed in many cell types, including lymphocytes. Fyn has been shown to interact with both the B cell and T cell receptor (BCR and TCR, respectively). While Fyn-deletion did not impair the development of immature T cells and B cells, TCR signaling was altered in mature T cells. Our results demonstrate that Fyn-KO mice have significantly low basal levels of IgG1 and IgG2a. Additionally, these mice displayed delayed kinetics in the production of NP-specific IgG1 and IgG2b, and significantly low NP-specific IgG2a after a T-dependent immunization protocol. Defects in antibody production correlated with significantly reduced numbers of GC B cells, TFH cells and splenic PCs. Moreover, Fyn-KO B cells showed decreased production antibody following in vitro activation. Our results thus demonstrate that Fyn-mediated signaling and B cell ADAM10 expression are necessary for optimal humoral responses.

Rights

© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

7-13-2012

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