Modulation of B cell responses by Toll-like receptors

Abstract

B lymphocytes are well known because of their key role in mediating humoral immune responses. Upon encounter with antigen and on cognate interaction with T cells, they differentiate into antibody-secreting plasma cells, which are critical for protection against a variety of pathogens. In addition to their antibody-production function, B cells are efficient antigen-presenting cells and express a variety of pathogen recognition receptors (PRRs). Engagement of these PRRs with their respective ligands results in cytokine and chemokine secretion and the upregulation of co-stimulatory molecules. These events constitute innate immune responses. Toll-like receptor (TLR) activation provides a third signal for B cell activation and is essential for optimal antigen-specific antibody responses. In some situations, TLR activation in B cells can result in autoimmunity. The purpose of this review is to provide some insights into the way that TLRs influence innate and adaptive B cell responses.

Altered Ig levels and antibody responses in mice deficient for the Fc receptor for IgM (FcμR)

“…Intact bacteria are complex particulate immunogens on which multiple proteins and polysaccharide Ags and TLR ligands (TLRLs) are coexpressed. TLRLs are well known to enhance immune responses, although the role of TLRs in B-cell activation and Ab production is not fully understood with conflicting results (41)(42)(43). The differences in TD Ab responses to R36A proteins versus NP-CGG in mutant mice might be due to the different antigenic forms, bacteria associated versus isolated.…”

B Cells: Programmers of CD4 T Cell Responses

“…B cells respond rapidly and robustly to stimulation via these receptors (see [20,[23][24][25] for reviews). Of the TLRs expressed by B cells, TLR4 and TLR9 (receptors for LPS and CpG respectively) have been the most extensively studied.…”

Toll-Like Receptors in the Pathogenesis of Autoimmune Diseases

“…3,4 These receptors are a family of type I transmembrane glycoproteins comprised of an extracellular domain with leucine-rich repeat (LRR) motifs, and a Toll/interleukin-1 receptor (IL-1R) -interacting (TIR) domain with at least 11 members in human and 13 in mouse, which leads to intracellular signaling and play an important role in both innate and acquired immune responses. [5][6][7] Each TLR is able to recognize a particular molecular pattern. For example, TLR2, 4, 5, 6 and 11 bind to bacterial membraneassociated molecules such as LPS, lipoprotein and peptidoglycan whereas TLR3, 7, 8 and 9 sense viral and bacterial or endogenous nucleic acids, including ssRNA, dsRNA, and unmethylated cytosine phosphate guanine (CpG) -containing DNA (Table 1).…”