Class switched memory B cell development and transcriptional programming is regulated by EZH2

Abstract

Abstract The most effective vaccines involve the development of antigen specific memory B cells (MBCs). MBCs make up a heterogenous population derived from germinal center (GC) dependent or independent processes, resulting in primarily immunoglobulin class switched and non-class switched MBCs, respectively. Class switched IgG MBCs are programmed to become plasma cells following a reinfection and non-class switched MBCs are programmed to seed secondary germinal centers. It is not clearly defined what epigenetic factors influence MBC differentiation and programming. EZH2 is a histone methyltransferase that catalyzes H3K27me3, resulting in gene repression. EZH2 has been shown to regulate multiple aspects of B cell differentiation, including development, germinal centers, and plasma cells; however, it is unknown if EZH2 regulates MBC development. To study EZH2, multiple knockout models have been established where EZH2 is conditionally deleted (cEZH2-KO). Here we used the influenza (PR8) model to determine the kinetics of antigen-specific MBC differentiation following a live infection in cEZH2-KO mice. We show that antigen positive MBCs are altered when EZH2 is deleted at days 14 and 39 post infection. Of the MBC subsets, IgG+, CD73+, and DP (PDL2+CD80+) MBCs were reliant on EZH2 for development but not IgM MBCs. These data indicate that extrafollicular/non-GC derived MBC differentiate in an EZH2-independent manner which reveals a distinct gene profile for extrafollicular/non-GC derived MBCs. EZH2 is necessary for repression of key gene regulators which determines the fate of class switched and non-switched MBCs. Overall, this model highlights the role of EZH2-dependent programming regarding MBC development and function. Supported by R01 AI148471 from NIH/NIAID to CDS