Toll-like receptor expression in the human nasopharyngeal tonsil (adenoid) and palantine tonsils: a preliminary report

Immune Stimulation with Imiquimod to Best Face SARS-CoV-2 Infection and Prevent Long COVID

Through widespread immunization against SARS-CoV-2 prior to or post-infection, a substantial segment of the global population has acquired both humoral and cellular immunity, and there has been a notable reduction in the incidence of severe and fatal cases linked to this virus and accelerated recovery times for those infected. Nonetheless, a significant demographic, comprising around 20% to 30% of the adult population, remains unimmunized due to diverse factors. Furthermore, alongside those recovered from the infection, there is a subset of the population experiencing persistent symptoms referred to as Long COVID. This condition is more prevalent among individuals with underlying health conditions and immune system impairments. Some Long COVID pathologies stem from direct damage inflicted by the viral infection, whereas others arise from inadequate immune system control over the infection or suboptimal immunoregulation. There are differences in the serum cytokines and miRNA profiles between infected individuals who develop severe COVID-19 or Long COVID and those who control adequately the infection. This review delves into the advantages and constraints associated with employing imiquimod in human subjects to enhance the immune response during SARS-CoV-2 immunization. Restoration of the immune system can modify it towards a profile of non-susceptibility to SARS-CoV-2. An adequate immune system has the potential to curb viral propagation, mitigate symptoms, and ameliorate the severe consequences of the infection.

[Microbiocenosis-regulating therapy of inflammatory pathology of the oropharynx]

Inflammatory pathology of the oropharynx, which does not lose its relevance, is a problem that is of interest to doctors of various specialties. As one of the main causes of inflammatory diseases of the pharynx, the influence of microorganisms, primarily viruses, on the mucous membrane of the upper respiratory tract is indicated. The authors of the article emphasize the importance of preserving the indigenous microbiota, which provides a barrier function and prevents the adhesion and colonization of pathogenic microorganisms. In this regard, the most effective and safe is local microbiocenosis-regulatory therapy using lysozyme, a natural peptide that has antiseptic, anti-inflammatory and immunoregulatory effects. As such a drug, the authors recommend the combined drug Lorolizin, which can be used in the treatment of acute pharyngitis, acute tonsillitis, and adenoiditis.

Altered tonsillar toll-like receptor (TLR)-1 and TLR-2 expression levels between periodic fever, aphthous stomatitis, pharyngitis and cervical adenitis (PFAPA), and group A beta-hemolytic streptococcal (GAβHS) recurrent tonsillitis patients

INTRODUCTION

Tonsillar microenvironment is thought to contribute to innate immune dysregulation responsible for the periodic fever, aphthous stomatitis, pharyngitis, and cervical adenitis (PFAPA) because of beneficial effects of tonsillectomy on treatment of the syndrome. Accordingly previous studies reported altered lymphocyte frequency, cytokine level and microbial composition in PFAPA tonsils. The aim of our study is to monitor expression levels of pro-inflammatory cell surface Toll-like receptors (TLRs) which have important role in induction of inflammation and maintaining tissue haemostasis.

MATERIALS AND METHODS

Seven patients with PFAPA syndrome, and eight patients with group A beta-hemolytic streptococcal (GAβHS) recurrent tonsillitis were included in our study. Tonsillar expression levels of TLR-1, -2, -4, -5, and -6 were monitored by immunohistochemistry (IHC). Expression levels were scored using semi-quantitative analysis method and were statistically analyzed by Two-Way Repeated Measures Analysis of Variance test.

RESULTS

IHC analysis demonstrated expression of all TLRs in tonsillar surface epithelium (SE) and lymphoid interior (LI) except for TLR-6 which was not present in the former. There has not been any statistically significant difference in TLR expression levels between PFAPA and GAβHS tonsils, except for TLR-1 and TLR-2 which were higher on LI and lower on SE of PFAPA tonsils, respectively, than that of the GAβHS samples.

CONCLUSIONS

Altered TLR expression levels may be involved in PFAPA pathogenesis. Future studies with higher patient number, uninflamed tonsils and cellular markers are required to further enlighten the role of TLRs in the development of syndrome.

Adenoidal Immune Response in the Context of Inflammation and Allergy

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The mucosal-associated lymphoid tissues of the upper respiratory tract, including adenoids and palatine tonsils, are considered as the first line of defense against respiratory infections, being important effector organs in both mucosal-type and systemic-type adaptive immunity. They are strategically located for mediating both local and regional immune functions, as they are exposed to antigens from both the inhaled air (allergens and pathogens) and the alimentary tract. Adenoids play a major role in the early and effective immune responses against viral and bacterial upper airway infections, as well as in the development of allergic reactions to respiratory allergens, being influenced by several environmental antigens and pollutants, such as tobacco smoke. In addition, recent studies have focused on new immune-modulating strategies for adenoidal cells as a preventive and therapeutic approach for chronic upper airways inflammation.

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Herein, we aimed to summarize what is known about the cellular and molecular mechanisms regulating adenoidal immune responses in the context of inflammation and allergy, with particular reference to scientific literature published within the last five years.

Expression of Innate Immunity Genes in Epithelial Cells of Hypertrophic Adenoids with and without Pediatric Chronic Rhinosinusitis: A Preliminary Report

BACKGROUND

Adenoid hypertrophy (AH) is associated with pediatric chronic rhinosinusitis (pCRS), but its role in the inflammatory process of pCRS is unclear. It is thought that innate immunity gene expression is disrupted in the epithelium of patients with chronic rhinosinusitis (CRS), including antimicrobial peptides and pattern recognition receptors (PRRs). The aim of this preliminary study was to detect the expression of innate immunity genes in epithelial cells of hypertrophic adenoids with and without pCRS to better understand their role in pCRS.

METHODS

Nine pCRS patients and nine simple AH patients undergoing adenoidectomy were recruited for the study. Adenoidal epithelium was isolated, and real-time quantitative polymerase chain reaction (RT-qPCR) was employed to measure relative expression levels of the following messenger RNAs in hypertrophic adenoid epithelial cells of pediatric patients with and without CRS: Human β-defensin (HBD) 2 and 3, surfactant protein (SP)-A and D, toll-like receptors 1-10, nucleotide-binding oligomerization domain (NOD)-like receptors NOD 1, NOD 2, and NACHT, LRR and PYD domains-containing protein 3, retinoic acid-induced gene 1, melanoma differentiation-associated gene 5, and nuclear factor-κB (NF-κB). RT-qPCR data from two groups were analyzed by independent sample t-tests and Mann-Whitney U-tests.

RESULTS

The relative expression of SP-D in adenoidal epithelium of pCRS group was significantly lower than that in AH group (pCRS 0.73 ± 0.10 vs. AH 1.21 ± 0.15; P = 0.0173, t = 2.654). The relative expression levels of all tested PRRs and NF-κB, as well as HBD-2, HBD-3, and SP-A, showed no statistically significant differences in isolated adenoidal epithelium between pCRS group and AH group.

CONCLUSIONS

Down-regulated SP-D levels in adenoidal epithelium may contribute to the development of pCRS. PRRs, however, are unlikely to play a significant role in the inflammatory process of pCRS.

Chronic tonsillitis is not associated with beta defensin 1 gene polymorphisms in Turkish population

BACKGROUND

Defensins are antimicrobial peptides expressed on mucosal surfaces. They function as part of the innate immune system. Palatine tonsils play important roles in innate immune system. However, our knowledge on the pathophysiology of chronic tonsils is limited.

OBJECTIVE

The aim of this study was to investigate the association between beta defensin 1 gene single nucleotide polymorphisms and chronic tonsillitis.

STUDY DESIGN

Prospective, non-randomized, controlled clinical study.

SETTING

Tertiary referral center.

SUBJECTS AND METHODS

Eighty six patients with chronic tonsillitis and eighty controls without history of chronic tonsillitis were enrolled in this study. Genotypes were determined by restriction fragment length polymorphism analyses after polymerase chain reaction.

RESULTS

Genotype and allele frequencies of the -20G/A (rs11362), -44C/G (rs1800972) and -52G/A (rs1799946) single nucleotide polymorphisms were not statistically different between patients and control groups (p>0.05).

CONCLUSION

In this study, we found that DEFB1 gene -20G/A, -44C/G and -52G/A single nucleotide polymorphisms were not associated with chronic tonsillitis. Studies, which analyse other polymorphism of the beta defensin 1 gene in large case series, should be conducted to understand the role of DEFB1 gene on chronic tonsillitis.

Functional effects of Toll-like receptor (TLR)3, 7, 9, RIG-I and MDA-5 stimulation in nasal epithelial cells

BACKGROUND

The human nasal epithelium is an important physical barrier, and a part of the innate immune defense that protect against pathogens. The epithelial cells recognize microbial components by pattern-recognition receptors (PRRs), and thereby trigger an immune response. Even though TLR3, TLR7, TLR9, RIG-I and MDA-5 are all known to respond to viral stimulation, their potential role in chronic airway inflammation triggered by local cytokine release remains to be established.

METHODS

mRNA and corresponding protein expression of TLR3, TLR7, TLR9, RIG-I and MDA-5 were analyzed in nasal biopsies and various upper airway epithelial cell lines using real-time reverse transcription PCR, immunohistochemistry and flow cytometry. Ligand induced, cytokine release, was evaluated with ELISA.

RESULTS

Nasal biopsies were found to express TLR3, TLR7, TLR9, RIG-I and MDA-5, with the most abundant expression in the surface epithelium. These receptors were verified in primary human nasal epithelial cell (HNEC) as well as in the airway epithelial cell lines Detroit-562 and FaDu. Poly(I:C) (TLR3) and R-837 (TLR7) stimulation increased secretion of IL-6 and GM-CSF from the nasal mucosa and the epithelial cell lines. CpG (TLR9) stimulation caused release of IL-8 in the nasal mucosa and in FaDu. Poly(I:C)/LyoVec (RIG-I/MDA-5) stimulation activated the secretion of IFN-β in the nasal mucosa. A corresponding release was also detected from HNEC and Detroit-562.

CONCLUSION

The nasal epithelium has the ability to recognize viral intrusion through TLR and RLR receptors, and the subsequent response might have a role in exacerbation of inflammatory diseases like allergic rhinitis and chronic rhinosinusitis.

Regulation of tight junctions in upper airway epithelium

The mucosal barrier of the upper respiratory tract including the nasal cavity, which is the first site of exposure to inhaled antigens, plays an important role in host defense in terms of innate immunity and is regulated in large part by tight junctions of epithelial cells. Tight junction molecules are expressed in both M cells and dendritic cells as well as epithelial cells of upper airway. Various antigens are sampled, transported, and released to lymphocytes through the cells in nasal mucosa while they maintain the integrity of the barrier. Expression of tight junction molecules and the barrier function in normal human nasal epithelial cells (HNECs) are affected by various stimuli including growth factor, TLR ligand, and cytokine. In addition, epithelial-derived thymic stromal lymphopoietin (TSLP), which is a master switch for allergic inflammatory diseases including allergic rhinitis, enhances the barrier function together with an increase of tight junction molecules in HNECs. Furthermore, respiratory syncytial virus infection in HNECs in vitro induces expression of tight junction molecules and the barrier function together with proinflammatory cytokine release. This paper summarizes the recent progress in our understanding of the regulation of tight junctions in the upper airway epithelium under normal, allergic, and RSV-infected conditions.

Why are East Asians more susceptible to several infection-associated cancers (carcinomas of the nasopharynx, stomach, liver, adenocarcinoma of the lung, nasal NK/T-cell lymphomas)?

There are at least five cancers with uniquely high incidence amongst East and Southeast Asian ethnic groups - namely nasopharyngeal carcinoma (NPC); gastric carcinoma; hepatocellular carcinoma (HCC); adeno-carcinoma of the lung in female non-smokers and nasal NK/T-cell lymphomas. They all appear to be related to an infective cause (Epstein Barr Virus, Helicobacter pylori, hepatitis B virus). We hypothesize that a genetic bottleneck 30,000years ago at the Last Glacial Maximum could have resulted in unique genetic polymorphisms in Toll-like receptor 8, making East Asians more vulnerable to these infective associated cancers. This bottleneck could have been caused by the presence of malaria in the southern Himalayan conduit between central and East Asia; and only those with an attenuated innate immune response to the malarial parasite (perhaps reflected by the TLR8 polymorphism) were spared the ravages of cerebral malaria; allowing these people to cross into east Asia, but then rendering them susceptible to later endemic infections and their associated cancers.

Retinoic acid-inducible gene 1-like receptors in the upper respiratory tract

BACKGROUND

Retinoic acid-inducible gene 1-like receptors (RLRs) are a novel family of pattern recognition receptors that include retinoic acid-inducible gene 1 (RIG-1), melanoma differentiation-associated gene 5 (MDA-5), and laboratory of genomics and physiology 2 (LGP-2). The knowledge of RLRs and their function in the human airway is limited. This study explores the role of RLRs in the upper respiratory tract.

METHODS

Tonsils, adenoids, nasal polyps, and biopsy specimens from the nasal mucosa were examined for the occurrence of the RIG-1, MDA-5, and LGP-2 using real-time reverse-transcription polymerase chain reaction and immunohistochemistry. The nasopharyngeal epithelial cell line FaDu was cultured with the RIG-1/MDA-5 ligand poly(I:C)/LyoVec (Invivogen, San Diego, CA) and analyzed for cytokine release using ELISA.

RESULTS

RIG-1, MDA-5, and LGP-2 mRNA were found in all tissues tested. The airway epithelium appeared to be their most prominent location. The RIG-1 and MDA-5 mRNA levels were higher in nasal polyps than in normal nasal mucosa, a state that seemed to be reversed by local steroid treatment. Culture of FaDu with poly(I:C)/LyoVec resulted in IL-6 and IL-8 release. No alteration in RLR expression in tonsils was seen on infection.

CONCLUSION

This study shows the presence and functional activity of RLRs in the human upper airways. It also suggests a role for RLRs in nasal polyposis.

Resilience and adaptation in the use of medicinal plants with suspected anti-inflammatory activity in the Brazilian Northeast

ETHNOPHARMACOLOGICAL RELEVANCE

This study uses the utilitarian redundancy model as a basis to investigate issues related to the preference for plants native to the Caatinga used as anti-inflammatories by respondents from the community of Carão in rural Pernambuco, Brazil.

MATERIALS AND METHODS

For this purpose, 49 respondents and 24 native plants used as anti-inflammatories were selected from a database built by previous studies in this study area. Interviews with respondents were conducted by applying the checklist-interview technique and by presenting photographs of plants, which were ordered according to plant preference for each type of inflammation mentioned. After elaborating each list of preferences, we inquired as to the criteria used for the construction of the lists. A salience index was calculated to determine the most- and least-preferred species, and principal component analysis (PCA) was used to identify the most significant criteria used by the respondents to indicate the preferred plants for anti-inflammatory use.

RESULTS

We identified 37 subcategories or inflammatory conditions, most of which were associated with disorders of the genitourinary (8 conditions), digestive (7) and respiratory (4) systems. Subcategories with the highest level of redundancy include "wound" (79.1% of species), "cut" (66.6%) and "uterus" (66.6%), and five non-redundant conditions were identified (only one species). We obtained approximately 300 lists and 18 choice criteria. PCA analysis showed that seven species were most preferred by the respondents, as they showed the highest salience values, and that the preferred criterion was "treatment effectiveness".

CONCLUSIONS

These results indicate that inflammation is a complex collection of disorders consisting of several subcategories. Furthermore, respondents preferred different treatments for different inflammatory conditions, which pose a challenge for future pharmacological studies that aim to assess the biological activity of anti-inflammatory plants. Preferences were very specific, focused on a small number of species and mainly related to therapeutic effectiveness.

NOD-like receptors in the human upper airways: a potential role in nasal polyposis

BACKGROUND

Nucleotide-binding oligomerization domain (NOD)-like receptors (NLRs) are newly discovered cytosolic receptors belonging to the pattern-recognition receptor family. They detect various pathogen-associated molecular patterns, triggering an immune response. The knowledge about these receptors, and their role in health and disease, is limited. The aim of the present study was to characterize the expression of NOD1, NOD2, and NALP3 in the human upper airways.

METHODS

Surgical samples were obtained from patients with tonsillar disease (n = 151), hypertrophic adenoids (n = 9), and nasal polyposis (n = 24). Nasal biopsies were obtained from healthy volunteers (n = 10). The expression of NOD1, NOD2, and NALP3 was analyzed using real-time PCR and immunohistochemistry.

RESULTS

Expression of NOD1, NOD2, and NALP3 mRNA and protein were seen in all tissue specimens. The NLR mRNA was found to be higher in nasal polyps than in normal nasal mucosa, and local steroid treatment reduced the NLR expression in polyps. In contrast, tonsillar infection with Streptococcus pyogenes or Haemophilus influenzae did not affect the NLR expression.

CONCLUSIONS

  The present study demonstrates the presence of NLRs in several upper airway tissues and highlights a potential role of NLRs in chronic rhinosinusitis with polyps.

Epithelial barrier and antigen uptake in lymphoepithelium of human adenoids

Invasion of antigens through the mucosal surface can be prevented by the common mucosal immune system, including Peyer's patches (PPs) and nasopharyngeal-associated lymphoreticular tissue (NALT). The adenoids (nasopharyngeal tonsils) comprise one of the NALTs and constitute the major part of Waldeyer's lymphoid ring in humans. However, the role of the lymphoepithelium, including M cells and dendritic cells (DCs), in the adenoids is unknown compared with the epithelium of PPs. NALTs also have unique functions such as the barrier of epithelial cells and uptake of antigens by M cells and DCs, and may play a crucial role in airway mucosal immune responses. The lymphoepithelium of adenoids has well-developed tight junctions that play an important role in the barrier function, the same as nasal epithelium but not palatine tonsillar epithelium. Tight junction molecules are expressed in both M cells and DCs as well as epithelial cells, and various antigens may be sampled, transported, and released to lymphocytes through the cells while they maintain the integrity of the epithelial barrier. This review summarizes the recent progress in our understanding of how M cells and DCs control the epithelial barrier in the adenoids.

Increased TLR7 expression in the adenoids among children with otitis media with effusion

CONCLUSION

Toll-like receptor 7 (TLR7) is present in the adenoids in young children and might play a role in the immunological response behind the development of otitis media with effusion (OME).

OBJECTIVES

To investigate the expression of the TLRs TLR4 and TLR7 in adenoids from children with OME and to compare the results with data obtained from healthy controls.

SUBJECTS AND METHODS

This was a controlled, prospective study. Eleven young children with long-standing OME and 10 controls with healthy middle ears were recruited consecutively when scheduled for adenoidectomy. mRNA was quantified using real-time polymerase chain reaction (PCR) and the localization of the corresponding proteins was assessed by immunohistochemistry.

RESULTS

mRNA for TLR4 and TLR7 could be obtained from all samples tested along with their corresponding proteins. The mRNA levels for TLR7 were increased among the children with a history of OME. No such increase was found for TLR4.

Psoriasis and streptococci: the natural selection of psoriasis revisited

We have previously postulated that surviving invasive streptococcal infections may have been a factor in psoriasis becoming a common skin disease in some parts of the world. Many of the candidate genes linked to psoriasis are associated with the acquired or innate immune system, which are also important in host defence to invasive streptococcal infections. High rates of positive streptococcal throat swabs among patients with chronic plaque psoriasis suggest that they are efficient at internalizing/carrying beta-haemolytic streptococci. Internalization of streptococci in the throat is dependent upon the transforming growth factor (TGF)-beta/fibronectin/alpha 5 beta 1 integrin pathway. The immune cell Th17 and its related cytokine network are important in mucosal defence, being very effective against extracellular microbes but having little effect on intracellular organisms. The TGF-beta/fibronectin/alpha 5 beta 1 integrin pathway and the Th17 cell network also appear to be operative in psoriasis, animal models of both TGF-beta and alpha 5 beta 1 cutaneous overexpression being associated with characteristic psoriasis lesions. We postulate that some of the genotypic/phenotypic changes in different immunological pathways in psoriasis, including the acquired T-cell response, the innate immune response, the TGF-beta/fibronectin/alpha 5 beta 1 integrin pathway and the Th17 cell system, confer protection against mortality during epidemics of invasive streptococcal infections, heightened efficiency in internalizing and allowing carriage of streptococci as well as predisposition to the development of psoriasis.

Expression of toll-like receptor 9 in peripheral blood mononuclear cells from patients with different hepatitis B and C viral loads

The aim of the present study was to investigate the expression of toll-like receptors (TLR) 9 in peripheral blood mononuclear cells (PBMC) of patients with chronic hepatitis B and C with different virus copies. The study group included 90 patients (60 with chronic hepatitis B, and 30 with chronic hepatitis C), and 20 healthy people served as control group. The protein and mRNA levels of TLR9 were detected by using flow cytometry and real-time PCR. The serum viral copies of HBV and HCV were measured in all patients, and the correlation between HBV-DNA copies or HCV-RNA copies and the TLR9 expression was analyzed. Our results demonstrated that HBV or HCV infection led to a decreased expression of TLR9 mRNA and protein compared to the control group (P<0.05). The TLR9 protein and mRNA levels were negatively correlated with serum viral copies of HBV and HCV (r=-0.632, r=-0.909, P<0.01). It was concluded that TLR9 mRNA and protein are down-regulated in PBMC of HBV-infected or HCV-infected patients, and they are negatively correlated with serum viral copies and play an important role in detecting viral replication of HBV and HCV.

Toll-like receptors in tonsillar epithelial cells

OBJECTIVE

The Waldeyer's ring, comprised of the nasopharyngeal tonsil, the paired tubal tonsils, the paired palatine tonsils, and the lingual tonsil, is arranged in a circular orientation around the wall of the throat. The location of the palatine tonsils, specifically, enables these structures to come in direct contact with potentially harmful inhaled and ingested material that exist in their native form since digestive enzymes are not present in the oral cavity. Thus, the tonsillar epithelium must not only serve a protective role but it must also function in an antigen-sampling role. Previous studies involving the tissues of the Waldeyer's ring have been focused on the adaptive immune system, with little consideration toward the innate immune system. Studies have demonstrated that the tonsils are capable of producing proinflammatory and antiviral cytokines and chemokines. In addition, other studies have highlighted the importance of epithelial cells in this response. Therefore, we postulate that toll-like receptors (TLRs), which recognize components of pathogenic organisms, may play a key role in the innate immune response in tonsillar epithelial cells. TLRs are innate pattern recognition receptors, which produce proinflammatory cytokines and chemokines upon ligation. In this study, we examine the expression and function of TLRs in the tonsillar epithelial cell lines, UT-SCC-60A and UT-SCC-60B. Additionally, we demonstrate successful isolation of primary tonsillar epithelial cells and examine TLR expression in these cells.

METHODS

We utilized endpoint RT-PCR, real time RT-PCR, and flow cytometric analysis to determine TLR expression. To assess TLR function, cells were stimulated with TLR ligands and supernatants were assayed for secretion of cytokines.

RESULTS

UT-SCC-60A and UTSCC-60B express TLR mRNA and TLR protein, and the observed responses to the TLR ligands, Pam3Cys and Poly I:C suggest that TLR2 and TLR3 are functional in these cells. Additionally, primary tonsillar epithelial cells express TLRs.

CONCLUSIONS

TLRs are expressed in human tonsillar epithelial cells and may play a vital role in the immunological outcomes in this tissue.

Toll-like receptor 7 and 9 expression in peripheral blood mononuclear cells from patients with chronic hepatitis B and related hepatocellular carcinoma

AIM

The aim of the present study was to investigate the expression of Toll-like receptors (TLR) 7 and 9 in peripheral blood mononuclear cells (PBMC) of patients with chronic hepatitis B virus (HBV) infection and related hepatocellular carcinoma.

METHODS

The study group was comprised of 52 patients: 41 with chronic hepatitis B and 11 healthy controls. The protein and mRNA levels of TLR7 and TLR9 were evaluated using real-time PCR, Western blot analysis, and flow cytometry. We also detected the serum viral load of HBV in the patients and analyzed the correlation between HBV-DNA copies and the TLR expression.

RESULTS

Our results demonstrated a lower TLR7 expression in all HBV infection groups compared to the controls. We found that HBV infection led to a decreased expression of TLR9 mRNA, but an increased expression of the TLR9 protein compared to the healthy group. The TLR protein levels are related to serum HBV-DNA (P<0.01).

CONCLUSION

There are downregulations of TLR7 expression and TLR9 mRNA in PBMC of HBV-infected patients, but an increased TLR9 expression at the protein level.

Toll-like receptor 2-mediated human B cell differentiation

Human B cells likely have a major role in the adjuvant activity of Toll-like receptor (TLR) 9 agonists by enhancing innate and adaptive immune responses. As several TLR2 ligands are promising vaccine adjuvant candidates, our aim was to characterize the effects of TLR2 stimulation on human B cell activation and differentiation using cells derived from healthy peripheral blood (PB), spleen, and diseased tonsils. We found a subset of partially differentiated TLR2+ PB and splenic B cells which responds to TLR2 agonists by mediating events involved in germinal center formation, such as upregulating CD77 and secreting chemokines. Furthermore, we show that TLR2-activated monocytes induce B cells to secrete significant quantities of IgM. Finally, activated TLR2+ B cells from tonsils are induced to secrete IgM directly by TLR2 ligands. Thus, TLR2 is likely involved in specific B cell-mediated functions and may be a viable vaccine adjuvant target in humans.