Toll-Like Receptor Expression and Responsiveness of Distinct Murine Splenic and Mucosal B-Cell Subsets

• Authors: Murali Gururajan, Emory University; Joshy Jacob, Emory University; Bali Pulendran, Emory University
• Journal Title: PLoS ONE
• Volume: Volume 2, Number 9
• Publisher: Public Library of Science | 2007, Pages e863-e863
• Type of Work: Article | Final Publisher PDF
• Publisher DOI: http://doi.org/10.1371/journal.pone.0000863
• Subjects: Biology, Microbiology; Health Sciences, Pathology; Health Sciences, Immunology

Abstract

Toll-like receptors (TLRs) are pattern recognition receptors that recognize pathogen associated molecular patterns and trigger innate immunity leading to initiation of adaptive immunity. TLR-mediated activation of dendritic cells (DCs) is known to be a critical event in the initiation of cellular and humoral immune responses. Recent work however suggests that B cells also express TLRs, and that they can be activated via TLR ligands. However, whether such B cell activation occurs only on memory B cells, or whether it can also occur on truly naïve B cells remains controversial. Furthermore, the expression and functional relevance of TLRs on distinct subsets of B cells, which are known to play differential roles in humoral responses is not known. Methodology/Principal Findings In this study, we investigated the expression pattern of different TLRs in distinct subsets of murine B cells (naïve, memory, follicular, marginal zone, B-1 and peyer's patch). In contrast to the reported restricted expression pattern of TLRs in human peripheral blood naïve B cells, murine splenic naïve B cells express a variety of TLRs with the exception of TLR5 and 8. Consistent with this relatively broad expression pattern, murine naive B cells proliferate and secrete antibody to a variety of TLR agonists in vitro, in the absence of B-cell receptor cross-linking. In addition, we observed subtle differences in the antibody secretion pattern of follicular, marginal zone, B-1 and peyer's patch B-cell subsets. Conclusions/Significance Thus various B cell subsets, including truly naïve B cells, express multiple TLRs, and signaling via such TLRs results in their robust proliferation and antibody secretion, even in the absence of dendritic cell activation, or T-cell help.