Memory B cells are instructed molecularly and epigenetically by CD4 T cells and EZH2 Restricted; Files Only
Keenan Wiggins (Fall 2024)
Abstract
Memory B cells (MBC) are a distinct class of differentiated B cells following activation by an antigen. This activation can occur naturally through pathogenic infections or by vaccination. The path to become an MBC requires transcriptional changes from their naïve B cell counterparts in a process called differentiation. Differentiation results in the gain or loss of gene expression to ensure that MBC acquire unique expression of hallmark genes involved in survival, migration, and rapid and robust reactivation. While much is known about the other subsets of B cells, molecular factors that aid in MBC formation and maintenance have been less studied. Here, the role of CD4 T cells, a class of T cells that provide signaling mechanisms to aid in the differentiation of B cells, and EZH2, the H3K27me3 methyltransferase, was investigated using genetically modified mice to globally delete the MHCII complex, leading to a loss of CD4 T cells, and conditionally delete EZH2 following a live influenza infection. Since MBC are long-lived two time points were used to look at early (14 days post infection) and late (39 days post infection) derived MBC. Deletion of CD4 T cells led to an overall decrease in MBC at both timepoints, specifically the class-switched and CD73+ subset of MBC. Deletion of EZH2 did not result in an overall reduction of MBC at either timepoint, but by the late timepoint MBC with class-switched BCR, CCR6+, and CD73+ surface markers were significantly reduced. The findings for loss of CD4 T cells were further investigated using an adoptive transfer of wild type and MHCII-KO B cells into a wild-type host to understand if the environment surrounding B cells can alter the programming following a loss of T: B cell interactions. The results were similar as above but by using RNA-seq the loss MHCII led to no significant MBC changes in gene expression compared to wild type MBC at day 14. Furthermore, all the MBC classes displayed a signature consistent with extrafollicular MBC and not germinal center derived MBC. Following up on the EZH2 deletion, RNA-seq and rechallenge experiments were performed to address the transcriptional landscape and function of MBC once EZH2 was deleted. The RNA-seq revealed a loss of repression in genes not normally expressed in MBC. Once MBC was formed and rechallenged with influenza, there was a reduction in the robustness of secondary germinal center B cells, antibody secreting cells, and MBC by 14 days post rechallenge. Taken together, this work identified CD4 T cells are not responsible for the formation of extrafollicular MBC and EZH2 positively regulates MBC formation and function.
Table of Contents
Table of Contents
Chapter 1. Introduction
Mechanisms of B cell Differentiation
Groundbreaking findings that enhance our comprehension of humoral immunity.
B cell differentiation
Memory differentiation occurs via distinct paths and stimuli.
Memory B cells are an essential component of B cell humoral response.
MBC can be separated based on different expression markers.
MBC formation from chronic infections.
MBC Transcriptome Reprogramming is Rapid and Progressive
Factors that instruct MBC formation and survival.
Epigenetic factors dictate B cell differentiation.
MBC formation requires epigenetic programming.
When is the memory fate imprinted?
Rationale and Overview
Chapter 2. Early influenza specific-memory B cells arise independently of CD4 T cell interactions
Abstract
Introduction
Results
Discussion
Methods
Chapter 3. EZH2 coordinates memory B cell programming and recall responses
Abstract
Introduction
Results
Discussion
SUPPORTING DATA
Materials and Methods
Chapter 4. Work in progress: The role of H3K27me3, timing of EZH2 activity, X31, and UTX in the maintenance and development of memory B cells
Chapter 5. Discussion
References
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File download under embargo until 09 January 2027 | 2024-12-02 11:19:02 -0500 | File download under embargo until 09 January 2027 |
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