Bioengineered Immune Organoids for Controlling B Cell Development
The humoral arm of the adaptive immune system works by producing antigen-specific antibody to clear pathogens from the extracellular spaces in the body. The humoral immunity requires the germinal center (GC) reaction to enable the formation of antibody-secreting cells and the production of antibodies that can bind the target antigen and trigger the appropriate immune responses. GC is a microanatomical structure in the B cell follicle that transiently arises from lymphocyte proliferation over the course of humoral immune response. While in vivo models have provided us with new insights regarding the GC reaction, there is a lack of ex vivo systems that can be utilized to model the GC process. Existing techniques do not fully recapitulate the lymphoid niche or require implantation into live animal models. It is thus challenging to assess the specific signals that control GC reaction, analyze the heterogeneous GC B cell population, and understand the decision-making process that determines GC B cell fate. In order to address these limitations, we have developed immune organoids to recapitulate key GC characteristics and control B cell activation in culture. We first analyzed the techniques that have been used to engineer B cell phenotype (Chapter 1). Inspired by the role of integrin in cell microenvironment, we utilized the gelatin matrix to enhance GC-like B cell expansion in culture (Chapter 2). We next showed that ex vivo GC-like B cells were comparable to in vivo GC B cells and could be used to study the GC cell cycle regulation (Chapter 3). We then used the modular immune organoid to assess the role of integrin ligand specificity in modulating GC-like B cell phenotype (Chapter 4). Finally, we demonstrated that B Cell Receptor (BCR) stimulation could induce ASC differentiation and facilitate the enrichment of antigen-specific GC-like B cells in the presence of a negative selection pressure (Chapter 5). Having described the works done to develop an improved B cell culture system, we concluded this dissertation with a reflection on the research journey and some suggestions regarding the next key steps to continue this project (Chapter 6). In the long term, we believe that the immune organoid platform could be used to obtain mechanistic insights about the adaptive immune system generation, understand the decision-making process in GC reaction, model lymphoid transformations that trigger certain diseases, and identify therapeutic agents that can interact with the immune system.
Biomedical engineering; 3D Cell Culture; B Cells; Germinal Center; Lymphoid Tissues; Tissue Engineering
August, Avery; Weiss, Robert S.; Putnam, David A.
PHD of Biomedical Engineering
Doctor of Philosophy
dissertation or thesis