Toll-like Receptor 1/2 Agonist Pam3CSK4 Suppresses Lipopolysaccharide-driven IgG1 Production while Enhancing IgG2a Production by B Cells

Abstract

Interaction between pathogen-associated molecular patterns and pattern recognition receptors triggers innate and adaptive immune responses. Several studies have reported that toll-like receptors (TLRs) are involved in B cell proliferation, differentiation, and Ig class switch recombination (CSR). However, roles of TLRs in B cell activation and differentiation are not completely understood. In this study, we investigated the direct effect of stimulation of TLR1/2 agonist Pam3CSK4 on mouse B cell viability, proliferation, activation, Ig production, and Ig CSR in vitro. Treatment with 0.5 µg/ml of Pam3CSK4 only barely induced IgG1 production although it enhanced B cell viability. In addition, high-dosage Pam3CSK4 diminished IgG1 production in a dose-dependent manner, whereas the production of other Igs, cell viability, and proliferation increased. Pam3CSK4 additively increased TLR4 agonist lipopolysaccharide (LPS)-induced mouse B cell growth and activation. However, interestingly, Pam3CSK4 abrogated LPS-induced IgG1 production but enhanced LPS-induced IgG2a production. Further, Pam3CSK4 decreased LPS-induced germline γ1 transcripts (GLTγ1)/GLTε expression but increased GLTγ2a expression. On the other hand, Pam3CSK4 had no effect on LPS-induced plasma cell differentiation. Taken together, these results suggest that TLR1/2 agonist Pam3CSK4 acts as a potent mouse B cell mitogen in combination with TLR4 agonist LPS, but these 2 different TLR agonists play diverse roles in regulating the Ig CSR of each isotype, particularly IgG1/IgE and IgG2a.

Dual TLR2/9 Recognition of Herpes Simplex Virus Infection Is Required for Recruitment and Activation of Monocytes and NK Cells and Restriction of Viral Dissemination to the Central Nervous System

“…This sequential recognition of HSV-1 must occur within the same DCs upon direct recognition of the virus and not through activation of bystander DCs ( 10 ). Similarly, it is thought that this sequential recognition of HSV-1 by TLR2 and TLR9 occurs in NK cells because TLR2 is expressed on the surface of NK cells, whereas TLR9 has an intracellular localization overlapping with the Golgi apparatus ( 60 , 61 ). Also, since TLR2 and TLR9 use the same adaptor molecule, MyD88, to transmit signals to a cascade of MAPKs that induces transcriptional expression of inflammatory cytokines ( 52 ), dual and sequential recognition of HSV-1 by TLR2 and TLR9 is assumed to amplify their intracellular signal in NK cells.…”

Effect of persimmon leaves (Diospyros kaki) on goblet cell density and inflammation in experimental dry eye model

“…Furthermore, the synthetic bacterial lipopeptide Pam3CSK4 is an effective activator of the NF-κB and IRF pathway. TLR-induced NF-κB and IRF signaling mediates the expression of pro-inflammatory factors including TNFα, IL-1β, IL-6, IL-8, C-C motif ligand-5 (CCL-5), and monocyte chemoattractant protein-1 (MCP-1) [45][46][47].…”

The Nod2 Agonist Muramyl Dipeptide Cooperates with the TLR4 Agonist Lipopolysaccharide to Enhance IgG2b Production in Mouse B Cells

“…The mouse B lymphoma cell line CH12F3-2A (surface μ + ) was provided by Dr. T. Honjo (Kyoto University, Kyoto, Japan). Mouse spleen resting B cells were obtained by depletion of CD43 + cells using anti-CD43 microbeads and high-gradient magnetic cell separation according to the manufacturer's instruction (MACS; Miltenyi Biotec, Bergisch Gladbach, Germany) as previously described [5]. The purity of resting B cells (CD43 − B220 + ) was assessed using FACSCalibur (BD Biosciences, San Jose, CA, USA) following staining of the cells with anti-CD43 FITC (eBioscience, San Diego, CA, USA) and anti-B220 PE (BD Biosciences) (Supplementary ).…”

“…TLR signaling can directly affect B cell functions, even without the support of T cells [1–4]. We recently reported that TLR1/2 agonist Pam3CSK4 and TLR7 agonist imiquimod directly inhibit IgG1 and IgE class switching, respectively, in activated mouse B cells [5, 6]. In addition, we found that Dectin-1 (a type of CLR) agonist selectively induced IgG1 class switching by TLR4 agonist lipopolysaccharide (LPS)-activated mouse B cells [7, 8].…”