CpG-A and CpG-B oligonucleotides differentially regulate MR1-mediated microbial Ag presentation

Abstract

Abstract Mucosal-associated invariant T (MAIT) cells are conserved innate T cells that express a semi-invariant T cell receptor (TCR; Vα7.2 in human and Vα19 in mice). MAIT cells are activated by microbial Ags presented by the major histocompatibility complex (MHC)-related molecule, MR1. Little is known how MR1 molecules are processed and loaded with microbial Ag in APCs. We have previously found that Toll-like Receptor 9 (TLR9) is important in regulating MR1-mediated bacterial Ag presentation to MAIT cells in B cells. We further demonstrated that, similar to human B cells, CpG-A (but not CpG-B) upregulated MR1 expression on mouse B cells as well. CpG-A treatment increased MR1 expression on WT mouse B cells but not MR1 KO B cells, further confirming that activation of B cells by CpG-A specifically enhances MR1 surface expression. Initial RNAseq analysis has indicated that B cells activated by CpG-A are distinctively different from those activated by CpG-B or the vehicle control. In conclusion, CpG-A and CpG-B differentially impact MR1 expression and microbial Ag presentation. We have successfully deleted the expression of TLR9 and its downstream mediators in a human B lymphoblastoid cell line (B-LCL) using CRISPR technology. Future work will focus on how genes altered by the activation of CpG-A (but not CpG-B) regulate MR1-mediated microbial Ag presentation.