Tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) in B-lymphocyte function

Immunomodulation by xylan and carrageenan-type polysaccharides from red seaweeds: Anti-inflammatory, wound healing, cytoprotective, and anticoagulant activities

The immunomodulatory properties of the polysaccharides (carrageenan, xylan) from Chondrus crispus (CC), Ahnfeltiopsis devoniensis (AD), Sarcodiotheca gaudichaudii (SG) and Palmaria palmata (PP) algal species were studied. Using RAW264.7 macrophages, we investigated the proliferation and migration capacity of different extracts along with their immunomodulatory activities, including nitric oxide (NO) production, phagocytosis, and secretion of pro-inflammatory cytokines. Polysaccharides from C. crispus and S. gaudichaudii effectively mitigated inflammation and improved scratch-wound healing. Polysaccharide fractions extracted under cold conditions (25 °C), including CC-1A, SG-1A and SG-1B stimulated cell proliferation, while fractions extracted under hot conditions (95 °C), including CC-3A, CC-2B and A. devoniensis (AD-3A), inhibited cell proliferation after 48 h. Furthermore, RAW264.7 cells treated with the fractions CC-3A, AD-1A, and SG-2A significantly reduced LPS-stimulated NO secretion over 24 h. Phagocytosis was significantly improved by treatment with C. crispus (CC-2B, CC-3B) and A. devoniensis (AD-3A) fractions. RAW264.7 cells treated with the CC-2A and SG-1A fractions showed elevated TGF-β1 expression without affecting TNF-α expression at 24 h. Polysaccharide fractions of A. devoniensis (ι/κ hybrid carrageenan; AD-2A, AD-3A) showed the highest anti-coagulation activity. CC-2A and SG-1A fractions enhanced various bioactivities, suggesting they are candidates for skin-health applications. The carrageenan fractions (CC-3A: λ-, μ-carrageenan, SG-2A: ν-, ι-carrageenan) tested herein showed great potential for developing anti-inflammatory and upscaled skin-health applications.

Tumor necrosis factor‑α in systemic lupus erythematosus: Structure, function and therapeutic implications (Review)

Tumor necrosis factor‑α (TNF‑α) is a pleiotropic pro‑inflammatory cytokine that contributes to the pathophysiology of several autoimmune diseases, such as multiple sclerosis, inflammatory bowel disease, rheumatoid arthritis, psoriatic arthritis and systemic lupus erythematosus (SLE). The specific role of TNF‑α in autoimmunity is not yet fully understood however, partially, in a complex disease such as SLE. Through the engagement of the TNF receptor 1 (TNFR1) and TNF receptor 2 (TNFR2), both the two variants, soluble and transmembrane TNF‑α, can exert multiple biological effects according to different settings. They can either function as immune regulators, impacting B‑, T‑ and dendritic cell activity, modulating the autoimmune response, or as pro‑inflammatory mediators, regulating the induction and maintenance of inflammatory processes in SLE. The present study reviews the dual role of TNF‑α, focusing on the different effects that TNF‑α may have on the pathogenesis of SLE. In addition, the efficacy and safety of anti‑TNF‑α therapies in preclinical and clinical trials SLE are discussed.

B Lineage Cells in ANCA-Associated Vasculitis

Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a systemic autoimmune disease that affects small sized blood vessels and can lead to serious complications in the lungs and kidneys. The prominent presence of ANCA autoantibodies in this disease implicates B cells in its pathogenesis, as these are the precursors of the ANCA-producing plasma cells (PCs). Further evidence supporting the potential role of B lineage cells in vasculitis are the increased B cell cytokine levels and the dysregulated B cell populations in patients. Confirmation of the contribution of B cells to pathology arose from the beneficial effect of anti-CD20 therapy (i.e., rituximab) in AAV patients. These anti-CD20 antibodies deplete circulating B cells, which results in amelioration of disease. However, not all patients respond completely, and this treatment does not target PCs, which can maintain ANCA production. Hence, it is important to develop more specific therapies for AAV patients. Intracellular signalling pathways may be potential therapeutic targets as they can show (disease-specific) alterations in certain B lineage cells, including pathogenic B cells, and contribute to differentiation and survival of PCs. Preliminary data on the inhibition of certain signalling molecules downstream of receptors specific for B lineage cells show promising therapeutic effects. In this narrative review, B cell specific receptors and their downstream signalling molecules that may contribute to pathology in AAV are discussed, including the potential to therapeutically target these pathways.

Roles of Suaeda vermiculata Aqueous-Ethanolic Extract, Its Subsequent Fractions, and the Isolated Compounds in Hepatoprotection against Paracetamol-Induced Toxicity as Compared to Silymarin

Suaeda vermiculata, a halophyte consumed by livestock, is also used by Bedouins to manage liver disorders. The aqueous-ethanolic extract of S. vermiculata, its subsequent fractions, and pure compounds, i.e., pheophytin-A (1), isorhamnetin-3-O-rutinoside (2), and quercetin (3), were evaluated for their hepatoprotective efficacy. The male mice were daily fed with either silymarin, plant aq.-ethanolic extract, fractions, pure isolated compounds, or carboxyl methylcellulose (CMC) for 7 days (n = 6/group, p.o.). On the day 7^th of the administrations, all, except the intact animal groups, were induced with hepatotoxicity using paracetamol (PCM, 300 mg/kg). The anesthetized animals were euthanized after 24 h; blood and liver tissues were collected and analysed. The serum aspartate transaminase (AST) and alanine transaminase (ALT) levels decreased significantly for all the S. vermiculata aq.-ethanolic extract, fraction, and compound-treated groups when equated with the PCM group (p < 0.0001). The antioxidant, superoxide dismutase (SOD), increased significantly (p < 0.05) for the silymarin-, n-hexane-, and quercetin-fed groups. Similarly, the catalase (CAT) enzyme level significantly increased for all the groups, except for the compound 2-treated group as compared to the CMC group. Also, the glutathione reductase (GR) levels were significantly increased for the n-butanol treated group than for the PCM group. The oxidative stress biomarkers, lipid peroxide (LP) and nitric oxide (NO), the inflammatory markers, IL-6 and TNF-α, and the kidney's functional biomarker parameters remained unchanged and did not differ significantly for the treated groups in comparison to the PCM-induced toxicity bearing animals. All the treated groups demonstrated significant decreases in cholesterol levels as compared to the PCM group, indicating hepatoprotective and antioxidant effects. The quercetin-treated group demonstrated significant improvement in triglyceride level. The S. vermiculata aq.-ethanolic extract, fractions, and the isolated compounds demonstrated their hepatoprotective and antioxidant effects, confirming the claimed traditional use of the herb as a liver protectant.

Discrimination of immune cell activation using Raman micro-spectroscopy in an in-vitro & ex-vivo model

Activation and proliferation of immune cells such as lymphocytes and monocytes are appropriate inflammatory responses to invading pathogens and are key to overcoming an infection. In contrast, uncontrolled and prolonged activation of these cellular signalling pathways can be deleterious to the body and result in the development of autoimmune conditions. The understanding of cellular activatory status therefore plays a significant role in disease diagnosis and progression. Conventional automated approaches such as enzyme linked immunosorbent assays (ELISA) and immune-labelling techniques are time-consuming and expensive, relying on a commercially available and specific antibody to identify cell activation. Developing a label-free method for assessing molecular changes would therefore offer a quick and cost-efficient alternative in biomedical research. Here Raman spectroscopy is presented as an effective spectroscopic method for the identification of activated immune cells using both cell lines and primary cells (including purified monocyte and lymphocyte subgroups and mixed peripheral blood mononuclear cell (PBMC) populations) obtained from healthy donors. All cell lines and primary cells were exposed to different stimulants and cellular responses confirmed by flow cytometry or ELISA. Machine learning models of cell discrimination using Raman spectra were developed and compared to reference flow-cytometry, with spectral discrimination levels comparing favourably with the reference method. Spectral signatures of molecular expression after activation were also extracted with results demonstrating alignment with expected profiles. High performance classification models constructed in these in-vitro and ex-vivo studies enabled identification of the spectroscopic discrimination of immune cell subtypes in their resting and activated state. Further spectral fitting analysis identified a number of potential spectral biomarkers that elucidate the spectral classification.

Eltrombopag second-line therapy in adult patients with primary immune thrombocytopenia in an attempt to achieve sustained remission off-treatment: results of a phase II, multicentre, prospective study

Up to 30% immune thrombocytopenia (ITP) patients achieve a sustained remission off-treatment (SROT) after discontinuation of thrombopoietin receptor agonists (TPO-RAs). Factors predictive of response are lacking. Patients aged ≥18 years with newly diagnosed or persistent ITP were treated with eltrombopag for 24 weeks. Primary end-point was SROT: the proportion of responders that were able to taper and discontinue eltrombopag maintaining the response during a period of observation (PO) of six months. Secondary end-points included the association between some immunological parameters (TPO serum levels, cytokines and lymphocyte subsets) and response. Fifty-one patients were evaluable. Primary end-point was achieved in 13/51 (25%) treated patients and 13/34 (38%) patients who started the tapering. Baseline TPO levels were not associated with response at week 24 nor with SROT. Higher baseline levels of IL-10, IL-4, TNF-α and osteopontin were negative factors predictive of response (P = 0·001, 0·008, 0·02 and 0·03 respectively). This study confirms that SROT is feasible for a proportion of ITP patients treated with eltrombopag. Some biological parameters were predictive of response.

Immune cell profiles associated with measured exposure to phthalates in the Norwegian EuroMix biomonitoring study - A mass cytometry approach in toxicology

BACKGROUND

Phthalate exposure has been associated with immune-related diseases such as asthma and allergies, but there is limited knowledge on mechanisms, effect biomarkers and thus biological support of causality.

OBJECTIVES

To investigate associations between exposure to the phthalates DEHP (di(2-ethylhexyl) phthalate) and DiNP (diisononyl phthalate) and functional immune cell profiles.

METHODS

Peripheral blood mononuclear cells (PBMCs) from 32 healthy adult Norwegian participants in the EuroMix biomonitoring study were selected based on high or low (n = 16) levels of urine metabolites of DEHP and DiNP. High-dimensional immune cell profiling including phenotyping and functional markers was performed by mass cytometry (CyTOF) using two broad antibody panels after PMA/ionomycin-stimulation. The CITRUS algorithm with unsupervised clustering was used to identify group differences in cell subsets and expression of functional markers, verified by manual gating.

RESULTS

The group of participants with high phthalate exposure had a higher proportion of some particular innate immune cells, including CD11c positive NK-cell and intermediate monocyte subpopulations. The percentage of IFNγ TNFα double positive NK cells and CD11b expression in other NK cell subsets were higher in the high exposure group. Among adaptive immune cells, however, the percentage of IL-6 and TNFα expressing naïve B cell subpopulations and the percentage of particular naïve cytotoxic T cell populations were lower in the high exposure group.

DISCUSSION

Cell subset percentages and expression of functional markers suggest that DEHP and DiNP phthalate exposure may stimulate subsets of innate immune cells and suppress adaptive immune cell subsets. By revealing significant immunological differences even in small groups, this study illustrates the promise of the broad and deep information obtained by high-dimensional single cell analyses of human samples to answer toxicological questions regarding health effects of environmental exposures.

Biocompatibility analysis of PLA based candidate materials for cardiovascular stents in a rat subcutaneous implant model

Modification of Polylactic acid (PLA), a biopolymer, is a strategy still to be fully explored for the next generation of bioresorbable vascular stent (BVS) biomaterials. With this focus, inclusions upto 5% of Polycaprolactone (PCL) and Magnesium in PLA were tested in the rat subcutaneous model and their cellular and tissue interactions characterized, specifically with respect to inflammatory response, angiogenesis and capsularization. The cytokines IL6, TNF Alpha and IL-1Beta were estimated in the peri-implant tissue, all of which showed a non-significant difference between the non-implanted animals and those containing PLA by 8 weeks, speaking to the benign nature of PLA as an implant biomaterial. Both modified materials, had increased macrophage counts and cytokine levels, except IL6 at 8 weeks. Vascularization only at 8 weeks in PLA PCL containing tissue was significantly higher than pure PLA, which may be more carefully controlled along with the material hydrophobicity for possible efforts towards therapeutic angiogenesis. Capsule thickness, measured by staining with both Hematoxylin & Eosin and Masson's Trichome did not show any differences between materials, including PLA.

Rotavirus VP6 Adjuvant Effect on Norovirus GII.4 Virus-Like Particle Uptake and Presentation by Bone Marrow-Derived Dendritic Cells In Vitro and In Vivo

We have previously shown that rotavirus (RV) inner capsid protein VP6 has an adjuvant effect on norovirus (NoV) virus-like particle- (VLP-) induced immune responses and studied the adjuvant mechanism in immortalized cell lines used as antigen-presenting cells (APCs). Here, we investigated the uptake and presentation of RV VP6 and NoV GII.4 VLPs by primary bone marrow-derived dendritic cells (BMDCs). The adjuvant effect of VP6 on GII.4 VLP presentation and NoV-specific immune response induction by BMDC in vivo was also studied. Intracellular staining demonstrated that BMDCs internalized both antigens, but VP6 more efficiently than NoV VLPs. Both antigens were processed and presented to antigen-primed T cells, which responded by robust interferon γ secretion. When GII.4 VLPs and VP6 were mixed in the same pulsing reaction, a subpopulation of the cells had uptaken both antigens. Furthermore, VP6 copulsing increased GII.4 VLP uptake by 37% and activated BMDCs to secrete 2-5-fold increased levels of interleukin 6 and tumor necrosis factor α compared to VLP pulsing alone. When in vitro-pulsed BMDCs were transferred to syngeneic BALB/c mice, VP6 improved NoV-specific antibody responses. The results of this study support the earlier findings of VP6 adjuvant effect in vitro and in vivo.

Differential Tick Salivary Protein Profiles and Human Immune Responses to Lone Star Ticks (Amblyomma americanum) From the Wild vs. a Laboratory Colony

Ticks are a growing concern to human and animal health worldwide and they are leading vectors of arthropod-borne pathogens in the United States. Ticks are pool blood feeders that can attach to the host skin for days to weeks using their saliva to counteract the host defenses. Tick saliva, as in other hematophagous arthropods, contains pharmacological and immunological active compounds, which modulate local and systemic immune responses and induce antibody production. In the present study, we explore differences in the salivary gland extract (SGE) protein content of Amblyomma americanum ticks raised in a laboratory colony (CT) vs. those collected in the field (FT). First, we measured the IgG antibody levels against SGE in healthy volunteers residing in Kansas. ELISA test showed higher IgG antibody levels when using the SGE from CT as antigen. Interestingly, antibody levels against both, CT-SGE and FT-SGE, were high in the warm months (May-June) and decreased in the cold months (September-November). Immunoblot testing revealed a set of different immunogenic bands for each group of ticks and mass spectrometry data revealed differences in at 19 proteins specifically identified in the CT-SGE group and 20 from the FT-SGE group. Our results suggest that differences in the salivary proteins between CT-SGE and FT-SGE may explain the differential immune responses observed in this study.

Family-based analyses reveal novel genetic overlap between cytokine interleukin-8 and risk for suicide attempt

BACKGROUND

Suicide is major public health concern. It is imperative to find robust biomarkers so that at-risk individuals can be identified in a timely and reliable manner. Previous work suggests mechanistic links between increased cytokines and risk for suicide, but questions remain regarding the etiology of this association, as well as the roles of sex and BMI.

METHODS

Analyses were conducted using a randomly-ascertained extended-pedigree sample of 1882 Mexican-American individuals (60% female, mean age = 42.04, range = 18-97). Genetic correlations were calculated using a variance components approach between the cytokines TNF-α, IL-6 and IL-8, and Lifetime Suicide Attempt and Current Suicidal Ideation. The potentially confounding effects of sex and BMI were considered.

RESULTS

159 individuals endorse a Lifetime Suicide Attempt. IL-8 and IL-6 shared significant genetic overlap with risk for suicide attempt (ρg = 0.49, pFDR = 7.67 × 10-03; ρg = 0.53, pFDR = 0.01), but for IL-6 this was attenuated when BMI was included as a covariate (ρg = 0.37, se = 0.23, pFDR = 0.12). Suicide attempts were significantly more common in females (pFDR = 0.01) and the genetic overlap between IL-8 and risk for suicide attempt was significant in females (ρg = 0.56, pFDR = 0.01), but not in males (ρg = 0.44, pFDR = 0.30).

DISCUSSION

These results demonstrate that: IL-8 shares genetic influences with risk for suicide attempt; females drove this effect; and BMI should be considered when assessing the association between IL-6 and suicide. This finding represents a significant advancement in knowledge by demonstrating that cytokine alterations are not simply a secondary manifestation of suicidal behavior, but rather, the pathophysiology of suicide attempts is, at least partly, underpinned by the same biological mechanisms responsible for regulating inflammatory response.

Is olive oil good for you? A systematic review and meta-analysis on anti-inflammatory benefits from regular dietary intake

The prevalence of non-communicable diseases is rapidly increasing, and evidence shows that diet and lifestyle are key areas of intervention to decrease their burden. Olive oil is considered one of the key nutritional components responsible for the benefits of the Mediterranean diet, which is characterized by the use of olive oil in meals as the main source of fat; a high consumption of water, fruits, nuts, vegetables, legumes, whole grains, spices, and herbs; a moderate consumption of dairy products (mainly cheese and yogurt), fish, poultry, and red wine; and a reduced consumption of red meat and processed foods. The aim of this review was to summarize evidence from randomized controlled trials on the effect of regular dietary intake of olive oil on three inflammatory markers: C-reactive protein, interleukin-6, and tumor necrosis factor-α. Reviewed RCTs reveal beneficial effects of olive oil by reducing levels of inflammation markers. Olive oil taken on a regular basis can be a good dietary fat alternative, especially to manage IL-6. However, further research is required to clarify the effects of olive oil consumption on inflammation, comparing to other fats. Moreover, olive oil daily dosage, different time-lenght intervention and follow-up periods should be taken into consideration.

Evaluation of the antirheumatic effects of isoflavone-free soy protein isolate and etanercept in rats with adjuvant-induced arthritis

IMPACT STATEMENT

In view of the partial clinical benefit and significant toxicity of traditional rheumatoid arthritis (RA) treatments, there is a growing trend to use complementary therapy. The antiarthritic activity of soy is related to the effect of soy isoflavones. However, little is known about the antiarthritic activity of soy protein itself. This study demonstrates that soy protein isolate (SPI) and etanercept (ETN), a tumor necrosis factor-α (TNF-α) inhibitor, protect rats against the effects of adjuvant-induced arthritis (AIA) by reducing inflammation (TNF-α and matrix metalloproteinase-3), autoantibody production (anticyclic citrullinated peptide), and lipid peroxidation (malondialdehyde). Only SPI improved dyslipidemia accompanied by RA, giving it the advantage of reducing cardiovascular risk. Additionally, the severity of arthritis-induced pathology, including inflammatory infiltrates, synovial hyperplasia, pannus formation, synovial vascularity, and cartilage erosions, was reduced by both SPI and ETN. This research ascertains the possible antiarthritic effect of SPI, making it a recommended alternative therapy for RA.

Novel Insights on the Regulation of B Cell Functionality by Members of the Tumor Necrosis Factor Superfamily in Jawed Fish

Most ligands and receptors from the tumor necrosis factor (TNF) superfamily play very important roles in the immune system. In particular, many of these molecules are essential in the regulation of B cell biology and B cell-mediated immune responses. Hence, in mammals, it is known that many TNF family members play a key role on B cell development, maturation, homeostasis, activation, and differentiation, also influencing the ability of B cells to present antigens or act as regulators of immune responses. Evolutionarily, jawed fish (including cartilaginous and bony fish) constitute the first animal group in which an adaptive immune response based on B cells and immunoglobulins is present. However, until recently, not much was known about the expression of TNF ligands and receptors in these species. The sequences of many members of the TNF superfamily have been recently identified in different species of jawed fish, thus allowing posterior analysis on the role that these ligands and receptors have on B cell functionality. In this review, we summarize the current knowledge on the impact that the TNF family members have in different aspects of B cell functionality in fish, also providing an in depth comparison with functional aspects of TNF members in mammals, that will permit a further understanding of how B cell functionality is regulated in these distant animal groups.

Protective Effects of Ellagitannin-Rich Strawberry Extracts on Biochemical and Metabolic Disturbances in Rats Fed a Diet High in Fructose

The present study compares the effects of two dietary strawberry extracts rich in monomeric (ME) or dimeric (DE) ellagitannins (ETs) on gastrointestinal, blood and tissue biomarkers in Wistar rats fed high-fructose diets. Both strawberry extracts beneficially affect the antioxidant status and lipid profile of the liver and serum. The ME extract shows a greater ability to inhibit lipid peroxidation in kidneys, more effectively decreases serum and liver triglycerides, and exerts greater anti-inflammatory effects in blood serum than the DE extract. The DE extract significantly reduces the activity of microbial enzymes in the cecum. These effects might be associated with higher cecum and urine levels of ET metabolites in rats fed with ME than in rats fed with DE. In conclusion, the diet-induced fructose-related disturbances observed in biochemical parameters are regulated by both extracts; nevertheless, the beneficial effects of the ME extract are mostly associated with systemic parameters, while those of the DE extracts are associated with local microbial activity.

Potential Role of Humoral IL-6 Cytokine in Mediating Pro-Inflammatory Endothelial Cell Response in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a multifactorial disease with limited therapeutic options. Numerous intrinsic and extrinsic factors are involved in ALS motor neuron degeneration. One possible effector accelerating motor neuron death in ALS is damage to the blood-Central Nervous System barrier (B-CNS-B), mainly due to endothelial cell (EC) degeneration. Although mechanisms of EC damage in ALS are still unknown, vascular impairment may be initiated by various humoral inflammatory factors and other mediators. Systemic IL-6-mediated inflammation is a possible early extrinsic effector leading to the EC death causing central nervous system (CNS) barrier damage. In this review, we discuss the potential role of humoral factors in triggering EC alterations in ALS. A specific focus was on humoral IL-6 cytokine mediating EC inflammation via the trans-signaling pathway. Our preliminary in vitro studies demonstrated a proof of principle that short term exposure of human bone marrow endothelial cells to plasma from ALS patient leads to cell morphological changes, significantly upregulated IL-6R immunoexpression, and pro-inflammatory cell response. Our in-depth understanding of specific molecular mechanisms of this humoral cytokine in EC degeneration may facilitate an endothelial-IL-6-targeting therapy for restoring cell homeostasis and eventually reestablishing B-CNS-B integrity in ALS.

Evaluating the longitudinal risk of social vigilance on atherosclerosis: study protocol for the North Texas Heart Study

INTRODUCTION

Psychosocial factors are increasingly recognised as important determinants of cardiovascular disease risk. The North Texas Heart Study aims to understand the mechanisms responsible for this association with a focus on social vigilance (ie, scanning the environment for social threats). There is also growing interest in supplementing traditional methods (eg, survey assessment of psychosocial risk paired with cross-sectional and longitudinal health outcomes) with daily or repeated momentary assessment of psychosocial factors. However, there are relatively few longitudinal studies directly comparing these approaches with hard endpoints.

METHODS AND ANALYSIS

The North Texas Heart Study proposes a longitudinal measurement burst design to examine psychosocial determinants of subclinical atherosclerosis. A sample of 300 healthy community participants, stratified by age and gender, will complete survey measures, as well as 2 days of ecological momentary assessment at baseline and at a 2-year follow-up. A range of psychosocial and behavioural factors, objective biomarkers, as well as carotid intima-media thickness (cIMT) will be assessed at both time points. Unadjusted and adjusted models will evaluate cross-sectional associations and determinants of change in the cIMT.

ETHICS AND DISSEMINATION

The Institutional Review Board at the study coordinating institute (University of North Texas) has approved this study. Positive, negative or inconclusive primary and ancillary findings will be disseminated in scientific journals and conferences.

Combination of poly I:C and Pam3CSK4 enhances activation of B cells in vitro and boosts antibody responses to protein vaccines in vivo

Vaccines that can rapidly induce strong and robust antibody-mediated immunity could improve protection from certain infectious diseases for which current vaccine formulations are inefficient. For indications such as anthrax and influenza, antibody production in vivo is a correlate of efficacy. Toll-like receptor (TLR) agonists are frequently studied for their role as vaccine adjuvants, largely because of their ability to enhance initiation of immune responses to antigens by activating dendritic cells. However, TLRs are also expressed on B cells and may contribute to effective B cell activation and promote differentiation into antigen-specific antibody producing plasma cells in vivo. We sought to discover an adjuvant system that could be used to augment antibody responses to influenza and anthrax vaccines. We first characterized an adjuvant system in vitro which consisted of two TLR ligands, poly I:C (TLR3) and Pam3CSK4 (TLR2), by evaluating its effects on B cell activation. Each agonist enhanced B cell activation through increased expression of surface receptors, cytokine secretion and proliferation. However, when B cells were stimulated with poly I:C and Pam3CSK4 in combination, further enhancement to cell activation was observed. Using B cells isolated from knockout mice we confirmed that poly I:C and Pam3CSK4 were signaling through TLR3 and TLR2, respectively. B cells activated with Poly I:C and Pam3CSK4 displayed enhanced capacity to stimulate allogeneic CD4⁺ T cell activation and differentiate into antibody-producing plasma cells in vitro. Mice vaccinated with influenza or anthrax antigens formulated with poly I:C and Pam3CSK4 in DepoVax^™ vaccine platform developed a rapid and strong antigen-specific serum antibody titer that persisted for at least 12 weeks after a single immunization. These results demonstrate that combinations of TLR adjuvants promote more effective B cell activation in vitro and can be used to augment antibody responses to vaccines in vivo.

Rotavirus Recombinant VP6 Nanotubes Act as an Immunomodulator and Delivery Vehicle for Norovirus Virus-Like Particles

We have recently shown that tubular form of rotavirus (RV) recombinant VP6 protein has an in vivo adjuvant effect on the immunogenicity of norovirus (NoV) virus-like particle (VLP) vaccine candidate. In here, we investigated in vitro effect of VP6 on antigen presenting cell (APC) activation and maturation and whether VP6 facilitates NoV VLP uptake by these APCs. Mouse macrophage cell line RAW 264.7 and dendritic cell line JAWSII were used as model APCs. Internalization of VP6, cell surface expression of CD40, CD80, CD86, and major histocompatibility class II molecules, and cytokine and chemokine production were analyzed. VP6 nanotubes were efficiently internalized by APCs. VP6 upregulated the expression of cell surface activation and maturation molecules and induced secretion of several proinflammatory cytokines and chemokines. The mechanism of VP6 action was shown to be partially dependent on lipid raft-mediated endocytic pathway as shown by methyl-β-cyclodextrin inhibition on tumor necrosis factor α secretion. These findings add to the understanding of mechanism by which VP6 exerts its immunostimulatory and immunomodulatory actions and further support its use as a part of nonlive RV-NoV combination vaccine.

The specialized proresolving mediator 17-HDHA enhances the antibody-mediated immune response against influenza virus: a new class of adjuvant?

Influenza viruses remain a critical global health concern. More efficacious vaccines are needed to protect against influenza virus, yet few adjuvants are approved for routine use. Specialized proresolving mediators (SPMs) are powerful endogenous bioactive regulators of inflammation, with great clinical translational properties. In this study, we investigated the ability of the SPM 17-HDHA to enhance the adaptive immune response using an OVA immunization model and a preclinical influenza vaccination mouse model. Our findings revealed that mice immunized with OVA plus 17-HDHA or with H1N1-derived HA protein plus 17-HDHA increased Ag-specific Ab titers. 17-HDHA increased the number of Ab-secreting cells in vitro and the number of HA-specific Ab-secreting cells present in the bone marrow. Importantly, the 17-HDHA-mediated increased Ab production was more protective against live pH1N1 influenza infection in mice. To our knowledge, this is the first report on the biological effects of ω-3-derived SPMs on the humoral immune response. These findings illustrate a previously unknown biological link between proresolution signals and the adaptive immune system. Furthermore, this work has important implications for the understanding of B cell biology, as well as the development of new potential vaccine adjuvants.

Anti-inflammatory effects of the neurotransmitter agonist Honokiol in a mouse model of allergic asthma

Chronic airway inflammation is a hallmark of asthma, an immune-based disease with great societal impact. Honokiol (HNK), a phenolic neurotransmitter receptor (γ-aminobutyric acid type A) agonist purified from magnolia, has anti-inflammatory properties, including stabilization of inflammation in experimentally induced arthritis. The present study tested the prediction that HNK could inhibit the chronic inflammatory component of allergic asthma. C57BL/6 mice sensitized to and challenged with OVA had increased airway hyperresponsiveness to methacholine challenge and eosinophilia compared with naive controls. HNK-treated mice showed a reduction in airway hyperresponsiveness as well as a significant decrease in lung eosinophilia. Histopathology studies revealed a marked drop in lung inflammation, goblet cell hyperplasia, and collagen deposition with HNK treatment. Ag recall responses from HNK-treated mice showed decreased proinflammatory cytokines in response to OVA, including TNF-α-, IL-6-, Th1-, and Th17-type cytokines, despite an increase in Th2-type cytokines. Regulatory cytokines IL-10 and TGF-β were also increased. Assessment of lung homogenates revealed a similar pattern of cytokines, with a noted increase in the number of FoxP3(+) cells in the lung. HNK was able to alter B and T lymphocyte cytokine secretion in a γ-aminobutyric acid type A-dependent manner. These results indicate that symptoms and pathology of asthma can be alleviated even in the presence of increased Th2 cytokines and that neurotransmitter agonists such as HNK have promise as a novel class of anti-inflammatory agents in the treatment of chronic asthma.

Accelerated atherosclerosis in systemic lupus erythematosus: role of proinflammatory cytokines and therapeutic approaches

Systemic lupus erythematosus (SLE), a chronic multisystem autoimmune disease with a broad range of clinical manifestations, is associated with accelerated atherosclerosis (AT) and increased risk of cardiovascular complications. Relevant factors directly influencing the development of AT comprise immune complex generation, complement activation, and changes in the production and activity of a complex network of cytokines, including type I and II interferons, B lymphocyte stimulator (BLyS), TNFα, IL-6, IL-17 and migration macrophage inhibitor (MIF). Autoantibodies, also responsible for cytokine expression and activation, play a supplementary key role in the development of AT. Genomic and proteomic studies have contributed to the discovery of genes and proteins involved in AT, including some that may be suitable to be used as biomarkers. All that data has allowed the development of new drugs, most of them evaluated in clinical trials: inhibitors of IFN and TNFα, B cell directed therapies, synthetic oligodeoxynucleotides, intravenous immunoglobulin, or statins. The focus of the present paper is to summarize recent evidence showing the role of cytokines in the development of AT in SLE and the rationale, and safety concerns, in the use of combined therapy to prevent AT and cardiovascular disease.

Honokiol, a Natural Plant Product, Inhibits Inflammatory Signals and Alleviates Inflammatory Arthritis

Honokiol (HNK), a phenolic compound isolated and purified from magnolia, has been found to have a number of pharmacologic benefits, including anti-angiogenic and anti-inflammatory properties. HNK has long been used in traditional Asian medicine without toxic side effects. We and others have extensively studied signaling to B cells by CD40 and its Epstein Barr viral mimic, latent membrane protein 1 (LMP1), which has been implicated in exacerbation of chronic autoimmune disease. We asked whether HNK could inhibit CD40 and LMP1 inflammatory signaling mechanisms. In vivo, HNK stabilized the severity of symptomatic collagen-induced arthritis in both CD40-LMP1 transgenic mice and their congenic C57BL/6 counterparts. Ex vivo studies, including collagen-specific serum Ab and Ag recall responses, as well as CD40 or LMP1-mediated activation of splenic B cells, supported the anti-inflammatory effects of HNK. In mouse B cell lines expressing the human CD40-LMP1 chimeric receptor, CD40- and LMP1-mediated NF-kappaB and AP-1 activation were abrogated in a dose-dependent manner, with a concomitant decrease in TNF-alpha and IL-6. These promising findings suggest that the nontoxic anti-inflammatory properties of HNK could be valuable for blocking the autoimmune response.

Monoclonal B-cell hyperplasia and leukocyte imbalance precede development of B-cell malignancies in uracil-DNA glycosylase deficient mice

Ung-deficient mice have reduced class switch recombination, skewed somatic hypermutation, lymphatic hyperplasia and a 22-fold increased risk of developing B-cell lymphomas. We find that lymphomas are of follicular (FL) and diffuse large B-cell type (DLBCL). All FLs and 75% of the DLBCLs were monoclonal while 25% were biclonal. Monoclonality was also observed in hyperplasia, and could represent an early stage of lymphoma development. Lymphoid hyperplasia occurs very early in otherwise healthy Ung-deficient mice, observed as a significant increase of splenic B-cells. Furthermore, loss of Ung also causes a significant reduction of T-helper cells, and 50% of the young Ung(-/-) mice investigated have no detectable NK/NKT-cell population in their spleen. The immunological imbalance is confirmed in experiments with spleen cells where the production of the cytokines interferon gamma, interleukin 6 and interleukin 2 is clearly different in wild type and in Ung-deficient mice. This suggests that Ung-proteins, directly or indirectly, have important functions in the immune system, not only in the process of antibody maturation, but also for production and functions of immunologically important cell types. The immunological imbalances shown here in the Ung-deficient mice may be central in the development of lymphomas in a background of generalised lymphoid hyperplasia.

Structure-based design and characterization of a Novel IL-6 antagonist peptide

The development of rational methods to design antagonist peptides based on the 3-D structure of protein active region has, to now, been only marginally successful. This has been largely due to the difficulty of constraining the recognition elements of a mimetic structure to the relative conformational and spatial orientations present in the parent molecule. According to the 3-D complex structure of human interleukin-6 (hIL-6) and its receptor (hIL-6R), a novel antagonist peptide (named PT), which possessed potential bioactivity of hIL-6, was designed by the means of distance geometry, molecular modeling and molecular dynamics trajectory analysis. The bioactivity of the designed peptide (i.e. PT) was evaluated using XG-7 cells, a hIL-6-dependent B-cell line. PT possessed potential bioactivity to antagonize the function of hIL-6 and could efficiently induce the growth arrest and apoptosis of XG-7 cells in a dose-dependent manner.

A novel hIL-6 antagonist peptide from computer-aided design contributes to suppression of apoptosis in M1 cells

Based on the complex crystal structure of human interleukin-6 (hIL-6) and its receptor (hIL-6R), a novel hIL-6 antagonist peptide (named PT) was designed using computer-guided design method. Dealing with molecular docking and molecular dynamics methods, the interaction between PT and hIL-6R was analyzed. The theoretical studies showed that PT possessed very high affinity to hIL-6R and offered a practical means of imposing long-term blockade of hIL-6 activity in vivo. This effect was examined due to growth arrest and apoptosis induced by hIL-6 in myeloblastic cell line M1 cells in a dose-dependent manner. The findings demonstrate that PT could also act as an excellent antagonist candidate for the induction of growth arrest and apoptosis. Furthermore, murine M1 myeloid cell line, which was induced by the physiological inducer hIL-6 to undergo apoptosis and growth arrest, could be used as a subtle model system to test hIL-6 antagonist.

Cytokine gene polymorphisms in endemic pemphigus foliaceus: a possible role for IL6 variants

Endemic pemphigus foliaceus (EPF) is a complex autoimmune disease characterized by the presence of antibodies against desmoglein 1, which lead to the loss of adhesion among keratinocytes (acantholysis). Variants of HLA class II genes have been the only genetic factors found to modulate susceptibility to EPF. This study aims at investigating the influence of cytokine genetic variants in the pathogenesis of EPF, since they may affect the expression levels of these immunomodulatory molecules. The sample included 168 patients and 189 controls and was comprised of mostly Caucasoids and Mulattos. The approach consisted of a case-control association study and the alleles were identified by mismatched PCR-RFLP. No associations were found with variants of IL1A, IL1B, IL1RN, IL4R and IL10. There was a weak negative association with the haplotype -1082G -592C (OR=0.49) of the IL10 gene in Mulattos. In regard to polymorphism -590 of the IL4 gene, a positive association with the T/T genotype (OR=2.71) and a negative association with the C variant (OR=0.37) were found. Associations with IL6 -174 variants suggest that the C/C genotype has a protective effect (OR=0.13) while carriers of the G allele are more susceptible (OR=7.66) to EPF.

The role of pathogenic B-cell clones in antibody mediated autoimmune disorders

Our understanding of the role of B-cells in the immunopathogenesis of certain antibody mediated diseases has developed remarkably in the past few years. In this review, autoantibody mediated immune disorders associated with pathogenic B-cell clones are discussed. We have focused on the roles and pathogenic mechanisms of B-cell clones in autoantibodyimmune diseases. The roles of pathogenic B-cells in Castleman's disease in PNP patients is used as one example. The developments in the treatment of B-cell mediated autoimmune diseases, such as intravenous immunoglobulin (IVIg), targets the regulatory pathway of B-cells, using anti-CD20, CD19, CD22 and, CD95 monoclonal antibody therapy, etc. are also discussed. Immunotherapy, targeting specific pathogenic B-cells, is believed to be one approach in the management of autoimmune diseases.

Role of tumor necrosis factor (TNF) receptor-associated factor 2 (TRAF2) in distinct and overlapping CD40 and TNF receptor 2/CD120b-mediated B lymphocyte activation

Members of the tumor necrosis factor receptor (TNFR) family play a variety of roles in the regulation of lymphocyte activation. An important TNFR family member for B cell activation is CD40. CD40 signals stimulate B cell TNF-alpha secretion, which subsequently signals via TNFR2 (CD120b) to enhance B cell activation. Although the function of the pro-apoptotic and pro-inflammatory receptor TNFR1 (CD120a) has been the subject of much research, less is understood about the distinct contributions of CD120b to cell activation and how it stimulates downstream events. Members of the tumor necrosis factor receptor family bind various members of the cytoplasmic adapter protein family, the tumor necrosis factor receptor-associated factors (TRAFs), during signaling. Both CD40 and CD120b bind TNF receptor-associated factor 2 (TRAF2) upon ligand stimulation. Wild type and TRAF2-deficient B cells expressing CD40 or the hybrid molecule (human) CD40 (mouse)-CD120b were examined. CD40- and CD120b-mediated IgM secretion were partly TRAF2-dependent, but only CD40 required TRAF2 for c-Jun N-terminal kinase activation. CD40 and CD120b used primarily divergent mechanisms to activate NF-kappaB, exemplifying how TNFR family members can use diverse mechanisms to mediate similar downstream events.

Distinct profiles of human B cell effector cytokines: a role in immune regulation?

There is growing interest in the fundamental roles that B cells may play in regulating immune responses. Emerging animal studies point to an important contribution of B cell effector cytokines to immune modulation, yet little is known about the factors regulating such cytokine production. We report that the profile of human B cell cytokine production is context dependent, being critically influenced by the balance of signals through the B cell receptor and CD40. B cells appropriately stimulated by sequential B cell receptor and CD40 stimulation proliferate and secrete TNF-alpha, lymphotoxin, and IL-6, which can act not only as autocrine growth and differentiation factors, but also serve to amplify the ongoing immune response. In contrast, CD40 stimulation alone, a mimic of a B cell receiving bystander T cell help in the absence of specific Ag recognition, induces negligible proinflammatory cytokines, but significant production of IL-10 that serves to suppress inappropriate immune responses. We thus describe a novel paradigm of reciprocal regulation of B cell effector cytokines, and ascribe active roles for human B cells in either promoting or suppressing local immune responses through context-dependent cytokine production.

The CTA1-DD vaccine adjuvant binds to human B cells and potentiates their T cell stimulating ability

The present study demonstrates that the novel CTA1-DD-adjuvant, which combines the full enzymatic activity of the A1 subunit of cholera toxin (CT) with an immunoglobulin-binding domain of Staphylococcus aureus protein A (SpA), binds directly to human peripheral blood B lymphocytes of all classes and greatly augments B cell functions in vitro. These effects were reflected in strongly enhanced co-stimulation, resulting in augmented T cell responses to polyclonal-specific as well as Ag-specific activation in vitro. The CTA1-DD-adjuvant had pronounced effects on B cell functions with up-regulated expression of several important activation and co-stimulatory molecules, in particular CD86. Moreover, the adjuvant alone promoted cytokine and chemokine secretion by targeted B cells and in the presence of additional stimuli proliferative responses were augmented. These effects were dependent on the whole enzymatically active CTA1-DD molecule, since DD alone had no effects on the B cells. Collectively our data suggest that CTA1-DD acted via enhanced co-stimulation, which holds promise as to the use of CTA1-DD as a non-toxic adjuvant in future vaccines for human use.

Development of an IL-6 antagonist peptide that induces apoptosis in 7TD1 cells

Interleukin-6 (IL-6) is a pleiotropic cytokine involved in the regulation of proliferation and differentiation of hematopoietic cells and in the pathogenesis of many diseases, including multiple myeloma. This study pursues a way to interfere with IL-6 pathway in an attempt to modulate its biological activity. Here we describe the rational design and biological evaluation of peptides able to antagonize the murine IL-6 activity by interfering with IL-6 Receptor alpha in 7TD1 cells, a IL-6-dependent B-cell line. Of the peptide tested, only Guess 4a is capable of interfering with IL-6 transducing pathway, therefore inducing growth arrest and apoptosis of 7TD1 cells.

A controlled trial of tick-borne encephalitis vaccination in patients with multiple sclerosis

The aim of this study was to investigate a possible link between a single vaccination against tick-borne encephalitis (TBE) and the appearance of one or more new cerebral lesions in magnetic resonance imaging (MRI) and/or a clinical relapse of MS. Fifteen MS patients with documented history of MS relapses living in a TBE endemic area were matched with 15 patients selected from a patient database containing 500 cases of MS. Three patients in each group were unvaccinated while all others had basic immunisation and regular booster vaccinations. Patients of the vaccination group received a single dose (3.3 microg) of a TBE vaccine. TBE antibodies were detected by ELISA and confirmed by neutralisation test. MRI was used as marker for disease activity and progression in addition to the clinical neurological examination. No association was seen between TBE vaccination and MRI detected disease activity, clinical relapse or disease progression of MS.

SLE - Complex cytokine effects in a complex autoimmune disease: tumor necrosis factor in systemic lupus erythematosus

Tumor necrosis factor (TNF) is a proinflammatory cytokine and a B-cell growth factor. It has numerous possible effects on T lymphocytes and dendritic cells, and it influences apoptosis. These differential effects may in part explain why patients under TNF-blocker therapy can develop autoantibodies to nuclear antigens, and may shed some light on the finding that low TNF fosters autoimmune disease in some mouse strains. On the contrary, TNF is increased in the blood and in the inflamed kidneys of systemic lupus erythematosus patients. Several studies in lupus-prone mice other than the F1 generation of New Zealand Black mice crossed with New Zealand White mice suggest that TNF is highly proinflammatory in the efferent limb and is potentially detrimental in lupus organ disease. Therefore, TNF blockade probably constitutes an efficacious therapeutic option.

Mechanisms for monocyte activation in co-culture with autologous tumor spheroids

Biopsies from carcinoma tissue and benign control mucosa from head and neck squamous cell carcinoma patients were used to establish fragment (F)-spheroids in vitro. We have previously shown that autologous monocytes co-cultured with F-spheroids in vitro secrete interleukin (IL)-6 upon 24h in co-culture. Presently, the aim was to study the mechanisms of this monocyte secretion. Paraformaldehyde (0.1% for 2min) or actinomycin-D (1 microg/ml for 24h) pre-treatment of the F-spheroids abolished the monocyte IL-6 co-culture response. Addition of glucose (100mM) or mannose (100mM), and to some extent galactose (100mM), but not fructose (100mM) to the co-cultures, partly inhibited the monocyte IL-6 co-culture response, but such addition did not inhibit the in vitro monocyte lipopolysaccharide (LPS)-generated IL-6 secretion. When mannose was added to the co-cultures, monocyte IL-6 mRNA expression was eradicated in malignant co-cultures and reduced to a low level in benign co-cultures. Addition of mouse anti-human beta(1)-integrin (anti-CD29) antibody (2 microg/ml) diminished the IL-6 co-culture response but not the monocyte LPS-generated IL-6 response. In conclusion, the monocyte IL-6 co-culture response is dependent on live spheroids and to some extent on direct contact with the F-spheroids, possibly via lectin-like receptor(s), the mannose receptor and beta(1)-integrin.

Oligodeoxynucleotides containing CpG motifs induce low levels of TNF-alpha in human B lymphocytes: possible adjuvants for Th1 responses

Oligodeoxynucleotides containing CpG motifs (CpG-ODN) represent potential adjuvants for specific immunotherapy of type I allergies because they foster Th1-like immune responses. However, previous work has shown that CpG-ODN induce systemically active levels of TNF-alpha in murine macrophages. The goal of the present study was to evaluate the release of TNF-alpha in human cells by a CpG-ODN proven to induce Th1 immune responses in cells from atopic individuals and in mice. CpG-ODN induced TNF-alpha in cells from atopic and healthy individuals. However, the amounts were low, as determined by comparison with commonly used Ags. Intracellular cytokine staining of PBMC revealed that CpG-ODN-induced TNF-alpha derived exclusively from B lymphocytes. TNF-alpha contributed to the CpG-ODN-augmented proliferation and Ig synthesis in PBMC, but was not involved in IFN-gamma synthesis. In conclusion, our findings indicate that certain CpG-ODN induce low amounts of TNF-alpha in human B lymphocytes and may therefore be used to modulate Th2-biased immune responses in allergic patients.

Inhibition of NF-κB induces apoptosis of KSHV-infected primary effusion lymphoma cells

Kaposi sarcoma–associated herpesvirus (KSHV), or human herpervirus 8 (HHV-8), is a γ-herpesvirus that infects human lymphocytes and is associated with primary effusion lymphoma (PEL). Currently, the role of viral infection in the transformation of PEL cells is unknown. One possibility is that KSHV, like the lymphotropic viruses Epstein-Barr virus (EBV) and human T-cell leukemia virus I (HTLV-I), activates the transcription factor NF-κB to promote survival and proliferation of infected lymphocytes. To examine this possibility, we assessed NF-κB activity in KSHV-infected PEL cell lines and primary tumor specimens by electrophoretic mobility shift assay (EMSA). We observed that NF-κB is constitutively activated in all KSHV-infected lymphomas, and consists of 2 predominant complexes, p65/p50 heterodimers and p50/p50 homodimers. Inhibition experiments demonstrated that Bay 11-7082, an irreversible inhibitor of IκBα phosphorylation, completely and specifically abrogated the NF-κB/DNA binding in PEL cells. PEL cells treated with Bay 11 demonstrated down-regulation of the NF-κB inducible cytokine interleukin 6 (IL-6), and apoptosis. These results suggest that NF-κB activity is necessary for survival of KSHV-infected lymphoma cells, and that pharmacologic inhibition of NF-κB may be an effective treatment for PEL.

Inhibition of NF-κB induces apoptosis of KSHV-infected primary effusion lymphoma cells

Kaposi sarcoma–associated herpesvirus (KSHV), or human herpervirus 8 (HHV-8), is a γ-herpesvirus that infects human lymphocytes and is associated with primary effusion lymphoma (PEL). Currently, the role of viral infection in the transformation of PEL cells is unknown. One possibility is that KSHV, like the lymphotropic viruses Epstein-Barr virus (EBV) and human T-cell leukemia virus I (HTLV-I), activates the transcription factor NF-κB to promote survival and proliferation of infected lymphocytes. To examine this possibility, we assessed NF-κB activity in KSHV-infected PEL cell lines and primary tumor specimens by electrophoretic mobility shift assay (EMSA). We observed that NF-κB is constitutively activated in all KSHV-infected lymphomas, and consists of 2 predominant complexes, p65/p50 heterodimers and p50/p50 homodimers. Inhibition experiments demonstrated that Bay 11-7082, an irreversible inhibitor of IκBα phosphorylation, completely and specifically abrogated the NF-κB/DNA binding in PEL cells. PEL cells treated with Bay 11 demonstrated down-regulation of the NF-κB inducible cytokine interleukin 6 (IL-6), and apoptosis. These results suggest that NF-κB activity is necessary for survival of KSHV-infected lymphoma cells, and that pharmacologic inhibition of NF-κB may be an effective treatment for PEL.

CD22 Cross-Linking Generates B-Cell Antigen Receptor-Independent Signals That Activate the JNK/SAPK Signaling Cascade

CD22 is a B-cell–specific adhesion molecule that modulates BCR-mediated signal transduction. Ligation of human CD22 with monoclonal antibodies (MoAbs) that block the ligand binding site triggers rapid tyrosine phosphorylation of CD22 and primary B-cell proliferation. Because extracellular signal-regulated kinases (ERKs) couple upstream signaling pathways to gene activation and are activated by B-cell antigen receptor (BCR) signaling, we examined whether CD22 ligation also activated ERKs and/or modified BCR-induced ERK activation. Ligation of CD22 on either primary B cells or B-cell lines failed to significantly activate the mitogen activated protein kinase (MAPK) ERK-2, but did activate the stress-activated protein kinases (SAPKs; c-jun NH2-terminal kinases or JNKs). In contrast, BCR ligation resulted in ERK-2 activation without significant SAPK activation. Concurrent ligation of CD22 and BCR enhanced BCR-mediated ERK-2 activation without appreciably modulating CD22-induced SAPK activation. Consistent with its induction of SAPK activity, there was a marked increase in nuclear extracts of activator protein-1 (AP-1) and c-jun levels within 2 hours of exposure of primary B cells to the CD22 MoAb. Despite their differences in ERK activation, both CD22 and BCR ligation triggered several Burkitt lymphoma cell lines to undergo apoptosis, and the 2 stimuli together induced greater cell death than either signal alone. The pro-apoptotic effects were CD22-blocking MoAb-specific and dose-dependent. Examination of expression levels of Bcl-2 protoncogene family members (Bcl-2, Bcl-xL, Mcl-1, and Bax) showed a downregulation of Bcl-xL and Mcl-1 after CD22 ligation. This study provides a plausible mechanism to explain how CD22 and BCR signaling can costimulate B-cell proliferation and induce apoptosis in Burkitt lymphoma cell lines.

CD22 Cross-Linking Generates B-Cell Antigen Receptor-Independent Signals That Activate the JNK/SAPK Signaling Cascade

CD22 is a B-cell–specific adhesion molecule that modulates BCR-mediated signal transduction. Ligation of human CD22 with monoclonal antibodies (MoAbs) that block the ligand binding site triggers rapid tyrosine phosphorylation of CD22 and primary B-cell proliferation. Because extracellular signal-regulated kinases (ERKs) couple upstream signaling pathways to gene activation and are activated by B-cell antigen receptor (BCR) signaling, we examined whether CD22 ligation also activated ERKs and/or modified BCR-induced ERK activation. Ligation of CD22 on either primary B cells or B-cell lines failed to significantly activate the mitogen activated protein kinase (MAPK) ERK-2, but did activate the stress-activated protein kinases (SAPKs; c-jun NH2-terminal kinases or JNKs). In contrast, BCR ligation resulted in ERK-2 activation without significant SAPK activation. Concurrent ligation of CD22 and BCR enhanced BCR-mediated ERK-2 activation without appreciably modulating CD22-induced SAPK activation. Consistent with its induction of SAPK activity, there was a marked increase in nuclear extracts of activator protein-1 (AP-1) and c-jun levels within 2 hours of exposure of primary B cells to the CD22 MoAb. Despite their differences in ERK activation, both CD22 and BCR ligation triggered several Burkitt lymphoma cell lines to undergo apoptosis, and the 2 stimuli together induced greater cell death than either signal alone. The pro-apoptotic effects were CD22-blocking MoAb-specific and dose-dependent. Examination of expression levels of Bcl-2 protoncogene family members (Bcl-2, Bcl-xL, Mcl-1, and Bax) showed a downregulation of Bcl-xL and Mcl-1 after CD22 ligation. This study provides a plausible mechanism to explain how CD22 and BCR signaling can costimulate B-cell proliferation and induce apoptosis in Burkitt lymphoma cell lines.