Toll-like receptor expression and responsiveness of distinct murine splenic and mucosal B-cell subsets.
BACKGROUND
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.


RESULTS
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
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.
Gururajan
Murali
M
Vaccine Research Center, Emory University, Atlanta, Georgia, United States of America.
Jacob
Joshy
J
Pulendran
Bali
B
D000818:Animals; D016175:B-Lymphocyte Subsets; D001402:B-Lymphocytes / Q000276:immunology*; D049109:Cell Proliferation; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D020869:Gene Expression Profiling; D007156:Immunologic Memory; D051379:Mice; D008810:Mice, Inbred C57BL; D009092:Mucous Membrane / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D016133:Polymerase Chain Reaction; D013154:Spleen / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D051193:Toll-Like Receptors / Q000235:genetics*
D051193:Toll-Like Receptors