RORα plays an important role in generation and maintenance of memory B cells

Abstract

Abstract Memory B cells (MBCs) are antigen-specific and long-lived. Upon reactivation, they can differentiate into plasma cells to secrete large amounts of high-affinity mostly class-switched antibodies. Prompted by our integrative analysis of the human MBC transcriptome and chromatin landscape which redundantly identified the transcriptional factor RORα as central to the identity of human class-switched (sw)MBCs, we investigated the contribution of RORα to the generation and maintenance of MBCs. We found that RORα is selectively expressed at a high level in both human and mouse swMBCs. We then constructed genetically modified AicdacreRorafl/flmice, in which RORα is specifically deleted in activated B cells undergoing class switching. Upon immunization with NP-CGG, AicdacreRorafl/flmice significantly reduced the generation of NP-specific swMBCs as part of a primary response otherwise without perturbation of germinal center formation, class-switch DNA recombination, somatic hypermutation or plasma cell differentiation, but leading to a defective anamnestic anti-NP-antibody response. To define the role of RORα in MBC maintenance, we generated tamoxifen-inducible B cell RORα conditional knockout CD19cre/ERT2Rorafl/flmice, in which RORα could be ablated in swMBCs already generated in response to immunization with NP-CGG. RORα ablation in swMBCs led to loss of swMBCs and the anamnestic anti-NP-response. Thus, B cell RORα plays an important role in not only the generation but also the maintenance of swMBCs. Further mechanistic insight in swMBC generation and maintenance will be provided by Cut&Tag and RNA-Seq experiments to identify sites of RORα enrichment across the genome and transcriptional targets of RORα in swMBCs. Supported by NIH grants AI 079705, AI 105813, AI 167416 and LRA grant 641363 to PC.