Characterization of class-switched B cells in chickens

While B cell development in the birds' primary B cell organ, the bursa Fabricius, is relatively well understood, very little is known about post bursal B cell differentiation into plasma and memory cells though these cells are essential for a protecting antibody response and so far, no specific markers for these cells were available. Since immunoglobulin class switch is one part of the B cell differentiation process, our objective was to conduct a first detailed investigation of class-switched chicken B cells. As only very few IgY and IgA expressing cells were detected in lymphoid organs of young chickens, we used CD40L and IL-10 to establish a prolonged in vitro culture system, which induces B cell proliferation, class switch to IgY and IgA and enhanced antibody secretion. This enabled a phenotypic analysis of differentiating B cells. Importantly, these cells lost surface expression of the B cell markers chB6 and BAFF-R. B cell receptor surface expression remained unchanged, showing that while differentiating toward plasma cells, B cells can be addressed by L chain staining. Newly generated potential plasma cell markers CD138 and TACI showed only a transient expression on cultured cells and rather act as markers for B cell activation than plasma/memory cells in general. CD57 upregulation was connected to activation and blast formation but not to class switch. We also examined potential changes in class-switched cells in different age groups and post vaccination. Surprisingly, bursa involution, laying and age had no distinct effects on the presence of class-switched cells, but we detected significantly more class-switched B cells post vaccination. Hence, we are now able to generate class-switched plasmablasts in vitro for a more detailed characterization and can address them under different conditions in chickens for further analysis of their B cell response.

Interleukin 6: at the interface of human health and disease

Interleukin 6 (IL-6) is a pleiotropic cytokine executing a diverse number of functions, ranging from its effects on acute phase reactant pathways, B and T lymphocytes, blood brain barrier permeability, synovial inflammation, hematopoiesis, and embryonic development. This cytokine empowers the transition between innate and adaptive immune responses and helps recruit macrophages and lymphocytes to the sites of injury or infection. Given that IL-6 is involved both in the immune homeostasis and pathogenesis of several autoimmune diseases, research into therapeutic modulation of IL-6 axis resulted in the approval of a number of effective treatments for several autoimmune disorders like neuromyelitis optica spectrum disorder (NMOSD), rheumatoid arthritis, juvenile idiopathic arthritis, polyarticular juvenile idiopathic arthritis, giant cell arteritis (GCA), and cytokine release syndrome, associated with SARS-CoV2 pneumonia. This review discusses downstream inflammatory pathways of IL-6 expression and therapeutic applications of IL-6 blockade, currently investigated for the treatment of several other autoimmune conditions such as autoimmune encephalitis, autoimmune epilepsy, as well as myelin oligodendrocyte glycoprotein associated demyelination (MOGAD). This review further highlights the need for clinical trials to evaluate IL-6 blockade in disorders such neuropsychiatric lupus erythematosus (SLE), sarcoidosis and Behcet's.

Role of IL-6 in the regulation of neuronal development, survival and function

The pleiotropic cytokine interleukin-6 (IL-6) is emerging as a molecule with both beneficial and destructive potentials. It can exert opposing actions triggering either neuron survival after injury or causing neurodegeneration and cell death in neurodegenerative or neuropathic disorders. Importantly, neurons respond differently to IL-6 and this critically depends on their environment and whether they are located in the peripheral or the central nervous system. In addition to its hub regulator role in inflammation, IL-6 is recently emerging as an important regulator of neuron function in health and disease, offering exciting possibilities for more mechanistic insight into the pathogenesis of mental, neurodegenerative and pain disorders and for developing novel therapies for diseases with neuroimmune and neurogenic pathogenic components.

Capsaicin Induces Apoptosis in KSHV-Positive Primary Effusion Lymphoma by Suppressing ERK and p38 MAPK Signaling and IL-6 Expression

Primary effusion lymphoma (PEL) is defined as a rare subtype of non-Hodgkin's B-cell lymphoma which is caused by Kaposi's sarcoma-associated herpesvirus (KSHV) in immunosuppressed patients. PEL is an aggressive lymphoma and is frequently resistant to conventional chemotherapies. Therefore, it is critical to investigate novel therapeutic options for PEL. Capsaicin is a pungent component of chili pepper and possesses unique pharmacological effects, such as pain relief, anti-microbial and anti-cancer properties. Here, we demonstrate that capsaicin markedly inhibited the growth of KSHV latently infected PEL cells by inhibiting ERK, p38 MAPK and expression hIL-6, which are known to contribute to PEL growth and survival. The underlying mechanism of action by capsaicin was through the inhibition of ERK and p38 MAPK phosphorylation and signaling that affected hIL-6 expression. As a result, capsaicin induced apoptosis in PEL cells in a caspase-9 dependent manner. In line with these results, ERK (U0126) and p38 MAPK (SB203580) specific signaling inhibitors suppressed hIL-6 expression and attenuated cell growth in PEL cells. Furthermore, the addition of hIL-6 neutralizing antibody to culture medium suppressed the growth of PEL cells. We also demonstrate that capsaicin suppressed PEL cell growth in the absence of nascent viral replication. Finally, we confirmed ex vivo treatment of capsaicin attenuated PEL development in SCID mice. Taken together, capsaicin could represent a lead compound for PEL therapy without the risk of de novo KSHV infection.

MAP Kinase Cascades in Antigen Receptor Signaling and Physiology

Mitogen-activated protein kinases (MAPKs) play roles in a cell type and context-dependent manner to convert extracellular stimuli to a variety of cellular responses, thereby directing cells to proliferation, differentiation, survival, apoptosis, and migration. Studies of genetically engineered mice or chemical inhibitors specific to each MAPK signaling pathway revealed that MAPKs have various, but non-redundant physiologically important roles among different families. MAPK cascades are obviously integrated in the B cell receptor signaling pathways as critical components to drive B cell-mediated immunity.

Rituximab plus liposomal doxorubicin in HIV-infected patients with KSHV-associated multicentric Castleman disease

Kaposi sarcoma (KS) herpesvirus-associated multicentric Castleman disease (KSHV-MCD) is a lymphoproliferative disorder, most commonly seen in HIV-infected patients, that has a high mortality if untreated. Concurrent KS is common. Although rituximab has reported activity in KSHV-MCD, its use is often associated with KS progression. Within a natural history study of KSHV-MCD, we prospectively evaluated rituximab 375 mg/m(2) combined with liposomal doxorubicin 20 mg/m(2) (R-Dox) every 3 weeks in 17 patients. Patients received a median of 4 cycles (range 3-9). All received antiretroviral therapy, 11 received consolidation interferon-α, and 6 received consolidation high-dose zidovudine with valganciclovir. Using NCI KSHV-MCD response criteria, major clinical and biochemical responses were attained in 94% and 88% of patients, respectively. With a median 58 months' potential follow-up, 3-year event-free survival was 69% and 3-year overall survival was 81%. During R-Dox therapy, cutaneous KS developed in 1 patient, whereas 5 of 6 patients with it had clinical improvement. R-Dox was associated with significant improvement in anemia and hypoalbuminemia. KSHV viral load, KSHV viral interleukin-6, C-reactive protein, human interleukin-6, and serum immunoglobulin free light chains decreased with therapy. R-Dox is effective in symptomatic KSHV-MCD and may be useful in patients with concurrent KS. This trial was registered at www.clinicaltrials.gov as #NCT00092222.

Recent advances in Kaposi sarcoma herpesvirus-associated multicentric Castleman disease

PURPOSE OF REVIEW

The discovery of Kaposi sarcoma herpesvirus (KSHV) led to recognition of KSHV-associated multicentric Castleman disease (MCD) as a distinct lymphoproliferative disorder. The pathogenesis of KSHV-MCD is attributed to proliferation of KSHV-infected B cells, production of KSHV-encoded viral interleukin 6 by these cells, and dysregulation of human interleukin 6 and interleukin 10. This article reviews advances in the field of disease pathogenesis and targeted therapies.

RECENT FINDINGS

Our understanding of the pathogenesis of KSHV-MCD has increased in recent years and improved therapies have been developed. Recent studies demonstrate that the anti-CD20 monoclonal antibody, rituximab, as well as virus-activated cytotoxic therapy using high-dose zidovudine and valganciclovir, can control symptoms and decrease adenopathy. With treatment, 1-year survival now exceeds 85%. Interestingly, even in the absence of pathologic findings of MCD, KSHV-infected patients may have inflammatory symptoms, excess cytokine production, and elevated KSHV viral load similar to KSHV-associated MCD. The term KSHV-associated inflammatory cytokine syndrome has been proposed to describe such patients.

SUMMARY

Recent advances in targeted therapy have improved outcomes in KSHV-MCD, and decreased need for cytotoxic chemotherapy. Improved understanding of the pathogenesis of KSHV-MCD and KSHV-associated inflammatory cytokine syndrome is needed, and will likely lead to additional advances in therapy for these disorders.

The role of synovial fluid markers of catabolism and anabolism in osteoarthritis, rheumatoid arthritis and asymptomatic organ donors

Introduction

The purpose of this study was to correlate the level of anabolic and catabolic biomarkers in synovial fluid (SF) from patients with rheumatoid arthritis (RA), patients with osteoarthritis (OA) and asymptomatic organ donors.

Methods

SF was collected from the knees of 45 OA, 22 RA patients and 20 asymptomatic organ donors. Eight biomarkers were selected and analyzed by using an enzyme-linked immunosorbent assay: interleukin (IL)-1, IL-6, IL-8 and IL-11; leukemia-inhibitory factor (LIF); cartilage oligomeric protein (COMP); osteocalcin; and osteogenic protein 1 (OP-1). Data are expressed as medians (interquartile ranges). The effects of sex and disease activity were assessed on the basis of the Western Ontario and McMaster Universities index score for patients with OA and on the basis of white blood cell count, erythrocyte sedimentation rate and C-reactive protein level for patients with RA.

Results

The mean ages (± SD) of the patients were as follows: 53 ± 9 years for patients with OA, 54 ± 11 years for patients with RA and 52 ± 7 years for asymptomatic organ donors. No effect of participants' sex was identified. In the SF of patients with RA, four of five cytokines were higher than those in the SF of patients with OA and those of asymptomatic organ donors. The most significant differences were found for IL-6 and IL-8, where IL-6 concentration in SF of patients with RA was almost threefold higher than that in patients with OA and fourfold higher than that in asymptomatic donor controls: 354.7 pg/ml (1,851.6) vs. 119.4 pg/ml (193.2) vs. 86.97 pg/ml (82.0) (P < 0.05 and P < 0.05, respectively). IL-8 concentrations were higher in SF of patients with RA than that in patients with OA as well as that in asymptomatic donor controls: 583.6 pg/ml (1,086.4) vs. 429 pg/ml (87.3) vs. 451 pg/ml (170.1) (P < 0.05 and P < 0.05, respectively). No differences were found for IL-11 in the SF of patients with RA and that of patients with OA, while a 1.4-fold difference was detected in the SF of patients with OA and that of asymptomatic donor controls: 296.2 pg/ml (257.2) vs. 211.6 pg/ml (40.8) (P < 0.05). IL-1 concentrations were the highest in the SF of RA patients (9.26 pg/ml (11.1)); in the SF of asymptomatic donors, it was significantly higher than that in patients with OA (9.083 pg/ml (1.6) vs. 7.76 pg/ml (2.6); P < 0.05). Conversely, asymptomatic donor control samples had the highest LIF concentrations: 228.5 pg/ml (131.6) vs. 128.4 pg/ml (222.7) in the SF of patients with RA vs. 107.5 pg/ml (136.9) in the SF of patients with OA (P < 0.05). OP-1 concentrations were twofold higher in the SF of patients with RA than those in patients with OA and threefold higher than those in asymptomatic donor control samples (167.1 ng/ml (194.8) vs. 81.79 ng/ml (116.0) vs. 54.49 ng/ml (29.3), respectively; P < 0.05). The differences in COMP and osteocalcin were indistinguishable between the groups, as were the differences between active and inactive OA and RA.

Conclusions

Activation of selected biomarkers corresponds to the mechanisms that drive each disease. IL-11, LIF and OP-1 may be viewed as a cluster of biomarkers significant for OA; while profiling of IL-1, IL-6, IL-8, LIF and OP-1 may be more significant in RA. Larger, better-defined patient cohorts are necessary to develop a biomarker algorithm for prognostic use.

IL-6 increases B-cell IgG production in a feed-forward proinflammatory mechanism to skew hematopoiesis and elevate myeloid production

Src homology 2 domain-containing inositol 5-phosphatase (SHIP(-/-)) animals display an age-related increase in interleukin-6 (IL-6), a decrease in B lymphopoiesis, and an elevation in myelopoiesis. We investigated the origin of the IL-6 production and show that it is largely produced by peritoneal and splenic macrophages. IL-6 production by these macrophages is not a direct result of the loss of SHIP: IL-6 production is not spontaneous, is absent from bone marrow-derived macrophages, declines with prolonged culture of macrophages, and requires a stimulus present in vivo. The IL-6-rich peritoneal cavity of SHIP(-/-) mice shows more than 700-fold more immunoglobulin G (IgG) than wild-type, approximately 20% of which is aggregated or in an immune complex and contains B220(+) cells that secrete IgG. The SHIP-deficient peritoneal macrophages show evidence of IgG receptor stimulation. Animals lacking both the signal-transducing gamma-chain of IgG receptors and SHIP or Ig and SHIP produce less IL-6. The data indicate a feed-forward process in which peripheral macrophages, responding through IgG receptors to secreted IgG, produce IL-6, to support further B-cell production of IgG. Because of the proinflammatory phenotype of SHIP(-/-) animals, these findings emphasize the importance of IL-6-neutralizing strategies in autoimmune and proinflammatory diseases.

Sialic acid reduces acute endotoxemia-induced liver dysfunction in the rat

Endotoxemia caused by LPS is a life-threatening and inflammatory condition contributing to multiple organ failure. Viruses or bacteria require sialic acid (SA) for target-cell binding. We suggest that exogenous SA through masking or mediating the binding of LPS to the target cells may attenuate LPS-induced liver dysfunction and cecal ligation and puncture-induced shock. We found that SA can directly scavenge O2-, H2O2, and NO activity by a chemiluminescence analyzer and bind to LPS with high affinity using surface plasmon resonance. Intravenous SA significantly increased plasma SA concentration within 4 h. We then assessed the potential effect of SA on LPS-induced acute endotoxemia in the rat. Intravenous LPS (10-50 mg/kg) dose-dependently increased plasma endotoxin and reactive oxygen species in the blood, bile, and liver and increased plasma alanine aminotransferase and aspartate aminotransferase levels as well as TNF-alpha, monocyte chemoattractant protein 1, tissue inhibitor of metalloproteinase 1, IL-1beta, and IL-6 levels in the rats. Thirty minutes after LPS stimulation, SA decreased LPS-enhanced endotoxin level, oxidative stress, alanine aminotransferase and aspartate aminotransferase levels, and cytokine concentration and ameliorated histopathologic alteration in the liver. We found that SA increased LPS-depressed Mn-superoxide dismutase, CuZn-superoxide dismutase, and heat shock protein 70 and decreased LPS-enhanced iNOS and proapoptotic Bax protein expression in the liver by Western blot. Sialic acid was given after treatment to rats subjected to cecal ligation and puncture, and the hypotensive effect was blunted for 6 h. In conclusion, SA treatment can counteract LPS-enhanced acute endotoxemia and oxidative injury via a direct scavenging reactive oxygen species activity and neutralization potential.

Pathogenesis of rheumatoid arthritis: targeting cytokines

Although considerable progress has been made by adequate treatment with traditional disease-modifying antirheumatic drugs (DMARDs), therapy of rheumatoid arthritis (RA) still remains difficult. The discovery of the importance of cytokines such as tumor necrosis factor (TNF), interleukin-1 (IL-1), interleukin-6 (IL-6), and interleukin-15 (IL-15), which are also stimulated by consequences of autoimmune responses, has led to the development of anticytokine therapies ("biologicals"). Blocking TNF or also, to some extent, IL-1 has proved beneficial in DMARD-resistant RA patients in multiple clinical trials. Along with clinical improvement, TNF blockade has been shown to halt radiographic disease progression, a major risk factor for disability. Recently, clinical trials have shown a significant therapeutic benefit of biological inhibitors of IL-6, and also of IL-15, with an efficacy comparable to that of TNF blockers. All these agents are particularly efficacious when combined with methotrexate. Although clinical remission is difficult to achieve even with anticytokine treatment, these drugs offer the potential to decrease disease activity and improve quality of life in a majority of RA patients, and it is conceivable that combinations of biological therapies may pave the path to even better success, which ultimately is remission or even cure.

Temperature alters lipopolysaccharide-induced cytokine secretion by RAW 264.7 cells

Local and systemic temperature change is associated with the immune response to infection, but the role of temperature remains poorly understood. To study the effect of temperature on macrophage activation by lipopolysaccharide (LPS), RAW 264.7 cells were incubated with LPS at different temperatures and secretion of three cytokines was measured. Incubation at 31 degrees C increased tumour necrosis factor (TNF) secretion when compared with 37 degrees C, while cells exposed at 39 degrees C secreted less TNF. Interleukin-6 (IL-6) secretion was less at 31 degrees C than at 37 degrees C and remained unchanged at 39 degrees C. Interleukin-10 secretion was depressed on either side of 37 degrees C. Only IL-6 secretion was sensitive to preincubation temperature effects. The kinetics of cytokine secretion and steady-state mRNA analysis indicated potentially different mechanisms of temperature regulation for TNF and IL-6.

Evidence of a trimolecular complex involving LPS, LPS binding protein and soluble CD14 as an effector of LPS response

The kinetics of the interaction of lipopolysaccharide (LPS), lipopolysaccharide binding protein (LBP) and CD14 was studied using surface plasmon resonance. The association and dissociation rate constants for the binding of LPS and rsCD14 were 2.9 x 10(4) M(-1) s(-1) and 0.07 s(-1) respectively, yielding a binding constant of 4.2 x 10(5) M(-1). Significantly, the presence of LBP increased not only the association rate but also the association constant for the interaction between LPS and CD14 by three orders of magnitude. Our experimental results suggest that LBP interacts with LPS and CD14 to form a stable trimolecular complex that has significant functional implications as it allows monocytes to detect the presence of LPS at a concentration as low as 10 pg/ml or 2 pM, and to respond by secreting interleukin-6. Thus, LBP is not merely transferring LPS to CD14 but it forms an integral part of the LPS-rLBP-rsCD14 complex.

STAT3 activation is required for interleukin-6 induced transformation in tumor-promotion sensitive mouse skin epithelial cells

STAT3, a member of signal transducers and activators of transcription (STATs) originally discovered as mediators in cytokine signaling pathways, plays an active role in oncogenesis. However, the function of STAT3 in signaling multistage carcinogenesis, especially in transformation of tumor-promotion sensitive epithelial cells has not been elucidated. The present study demonstrates that STAT3 is activated in interleukin-6 induced transformation in mouse skin epithelial cells. DNA binding and transcriptional activities of STAT3 were significantly increased by interleukin-6. This induced anchorage-independent transformation in tumor-promotion sensitive JB6 mouse skin P+ cells but not in the resistant variant P- cells. Two forms of dominant negative STAT3 (mutant of transcriptional domain, mF, or DNA-binding domain, mD) were stably transfected into P+ cells. Activation of STAT3 was abolished and importantly, interleukin-6 induced anchorage-independent growth was absent in both mutant STAT3 transfectants. To determine the genes targeted by STAT3, three matrix metalloproteinase proteins linked with carcinogenesis of epithelial cells were analysed. Both basal and interleukin-6 induced expression of collagenase I and stromelysin I, but not gelatinase A, were inhibited in the mutant STAT3 transfectants. Furthermore, transfection of a wild type STAT3 restored STAT3 transactivation and response to interleukin-6 induced transformation in mutant STAT3 transfectants, which up-regulated collagenase I and stromelysin I as well. Together, these results provide the first evidence that STAT3 activation is required in the progression of multistage carcinogenesis of mouse skin epithelial cells, and matrix metalloproteinases are actively involved in STAT3-mediated cell transformation.

Interleukin-6 regulation of the human DNA methyltransferase (HDNMT) gene in human erythroleukemia cells

Methylation of mammalian DNA by the DNA methyltransferase enzyme (dnmt-1) at CpG dinucleotide sequences has been recognized as an important epigenetic control mechanism in regulating the expression of cellular genes (Yen, R. W., Vertino, P. M., Nelkin, B. D., Yu, J. J., el-Deiry, W., Cumaraswamy, A., Lennon, G. G., Trask, B. J., Celano, P., and Baylin, S. B. (1992) Nucleic Acids Res. 20, 2287-2291; Ramchandani, S., Bigey, P., and Szyf, M. (1998) Biol. Chem. 379, 535-5401). Here we show that interleukin (IL)-6 regulates the methyltransferase promoter and resulting enzyme activity, which requires transcriptional activation by the Fli-1 transcription factor (Spyropoulos, D. D., Pharr, P. N., Lavenburg, K. R., Jackers, P., Papas, T. S., Ogawa, M., and Watson, D. K. (1998) Mol. Cell. Biol. 15, 5643-5652). The data suggest that inflammatory cytokines such as IL-6 may exert many epigenetic changes in cells via the regulation of the methyltransferase gene. Furthermore, IL-6 regulation of transcription factors like Fli-1, which can help to direct cells along opposing differentiation pathways, may in fact be reflected in part by their ability to regulate the methylation of cellular genes.

Activation-induced inhibition of interleukin 6-mediated T cell survival and signal transducer and activator of transcription 1 signaling

The cytokines interleukin (IL)-2, IL-4, IL-6, IL-7, and IL-15 have all previously been shown to inhibit resting T cell death in vitro. We have found a difference in the response of T cells to IL-6, depending on the activation status of the cells. IL-6 inhibited the death of naive T cells, but had no effect on the death of either superantigen-activated T cells, or T cells bearing memory markers. This was true even when the resting and activated T cells were isolated from the same animal; thus, the determining factor for IL-6 insensitivity was the activation status or activation history of the cell, and not the milieu in the animal from which the cells were isolated. Activated T cells expressed lower levels of IL-6 receptors on their surfaces, yet there were sufficient levels of receptors for signaling, as we observed similar levels of signal transducer and activator of transcription (Stat)3 phosphorylation in resting and activated T cells treated with IL-6. However, there was profound inhibition of IL-6-induced Stat1 phosphorylation in activated T cells compared with resting T cells. These data suggest that there is activation-induced inhibition of IL-6 receptor signaling in T cells. This inhibition appears to be specific for some but not all of the IL-6-mediated signaling cascades in these cells.

Involvement of Interleukin-10 (IL-10) and Viral IL-6 in the Spontaneous Growth of Kaposi’s Sarcoma Herpesvirus-Associated Infected Primary Effusion Lymphoma Cells

Primary effusion lymphoma (PEL) is a distinct type of lymphoma associated with Kaposi’s sarcoma-associated herpesvirus (KSHV) infection. To determine the factors responsible for the unrestrained proliferation of PEL, we have studied the growth factor requirements of the PEL-derived BCBL-1 and BC-1 cell lines. Both cell lines were found to be autocrine growth factor dependent and to release human interleukin-6 (IL-6), viral IL-6 (vIL-6), and human IL-10 in the culture supernatant. To establish whether these cytokines contribute to autocrine growth, neutralizing antibodies against human IL-6, vIL-6, human IL-10, and soluble IL-10 receptor were used. These experiments showed that human IL-10 and, to a lesser degree, vIL-6 serve as autocrine growth factors for BCBL-1 and BC-1 cells. Thus, human IL-10 and vIL-6 are growth factors released and used by PEL cells for autonomous proliferation and may be critical to the development and progression of PEL.

Involvement of Interleukin-10 (IL-10) and Viral IL-6 in the Spontaneous Growth of Kaposi’s Sarcoma Herpesvirus-Associated Infected Primary Effusion Lymphoma Cells

Primary effusion lymphoma (PEL) is a distinct type of lymphoma associated with Kaposi’s sarcoma-associated herpesvirus (KSHV) infection. To determine the factors responsible for the unrestrained proliferation of PEL, we have studied the growth factor requirements of the PEL-derived BCBL-1 and BC-1 cell lines. Both cell lines were found to be autocrine growth factor dependent and to release human interleukin-6 (IL-6), viral IL-6 (vIL-6), and human IL-10 in the culture supernatant. To establish whether these cytokines contribute to autocrine growth, neutralizing antibodies against human IL-6, vIL-6, human IL-10, and soluble IL-10 receptor were used. These experiments showed that human IL-10 and, to a lesser degree, vIL-6 serve as autocrine growth factors for BCBL-1 and BC-1 cells. Thus, human IL-10 and vIL-6 are growth factors released and used by PEL cells for autonomous proliferation and may be critical to the development and progression of PEL.

Angiogenesis and Hematopoiesis Induced by Kaposi’s Sarcoma-Associated Herpesvirus-Encoded Interleukin-6

Kaposi’s sarcoma-associated herpesvirus (KSHV; also known as human herpesvirus 8 [HHV-8]) is a herpesvirus linked to the development of Kaposi’s sarcoma (KS), primary effusion lymphoma, and a proportion of Castleman’s disease. KSHV encodes viral interleukin-6 (vIL-6), which is structurally homologous to human and murine IL-6. The biological activities of vIL-6 are largely unknown. To gain insight into the biology of vIL-6, we expressed vIL-6 in murine fibroblasts NIH3T3 cells and inoculated stable vIL-6–producing clones into athymic mice. vIL-6 was detected selectively in the blood of mice injected with vIL-6–expressing clones. Compared with controls, vIL-6–positive mice displayed increased hematopoiesis in the myeloid, erythroid, and megakaryocytic lineages; plasmacytosis in spleen and lymph nodes; hepatosplenomegaly; and polyclonal hypergammaglobulinemia. vIL-6–expressing NIH3T3 cells gave rise to tumors more rapidly than did control cells, and vIL-6–positive tumors were more vascularized than controls. Vascular endothelial growth factor (VEGF) was detected at higher levels in the culture supernatant of vIL-6–expressing cells compared with controls, and immunohistochemical staining detected VEGF in spleen, lymph nodes, and tumor tissues from mice bearing vIL-6–producing tumors but not control tumors. Thus, vIL-6 is a multifunctional cytokine that promotes hematopoiesis, plasmacytosis, and angiogenesis. Through these functions, vIL-6 may play an important role in the pathogenesis of certain KSHV-associated disorders.

Angiogenesis and Hematopoiesis Induced by Kaposi’s Sarcoma-Associated Herpesvirus-Encoded Interleukin-6

Kaposi’s sarcoma-associated herpesvirus (KSHV; also known as human herpesvirus 8 [HHV-8]) is a herpesvirus linked to the development of Kaposi’s sarcoma (KS), primary effusion lymphoma, and a proportion of Castleman’s disease. KSHV encodes viral interleukin-6 (vIL-6), which is structurally homologous to human and murine IL-6. The biological activities of vIL-6 are largely unknown. To gain insight into the biology of vIL-6, we expressed vIL-6 in murine fibroblasts NIH3T3 cells and inoculated stable vIL-6–producing clones into athymic mice. vIL-6 was detected selectively in the blood of mice injected with vIL-6–expressing clones. Compared with controls, vIL-6–positive mice displayed increased hematopoiesis in the myeloid, erythroid, and megakaryocytic lineages; plasmacytosis in spleen and lymph nodes; hepatosplenomegaly; and polyclonal hypergammaglobulinemia. vIL-6–expressing NIH3T3 cells gave rise to tumors more rapidly than did control cells, and vIL-6–positive tumors were more vascularized than controls. Vascular endothelial growth factor (VEGF) was detected at higher levels in the culture supernatant of vIL-6–expressing cells compared with controls, and immunohistochemical staining detected VEGF in spleen, lymph nodes, and tumor tissues from mice bearing vIL-6–producing tumors but not control tumors. Thus, vIL-6 is a multifunctional cytokine that promotes hematopoiesis, plasmacytosis, and angiogenesis. Through these functions, vIL-6 may play an important role in the pathogenesis of certain KSHV-associated disorders.

Neonatal Murine B Lymphocytes Respond to Polysaccharide Antigens in the Presence of IL-1 and IL-6

Unlike adults, neonates are unable to respond to polysaccharide Ags, making them especially vulnerable to pathogenic encapsulated bacteria. Since the Ab response to polysaccharides in adult mice requires certain cytokines, it was hypothesized that neonatal murine B cells may be competent to respond to such Ags, but may fail to do so due to a deficiency of cytokines. Neonatal splenocyte cultures, which were otherwise unresponsive to trinitrophenyl (TNP)-Ficoll, a haptenated polysaccharide Ag, mounted an adult-like Ab response when supplemented with IL-1. However, IL-1 failed to induce such a response to TNP-Ficoll when purified B cells were used instead. Although IL-6 alone did not induce a response in whole spleen cells or purified B cells from neonates, it synergized with IL-1 in inducing purified neonatal B cells to respond to TNP-Ficoll. The avidity of the cytokine-induced neonatal anti-TNP Abs was comparable to that of Abs made by adult splenocyte cultures. One effect of IL-1 may be at the level of clonal expansion, since it induced neonatal B cells to proliferate in response to anti-IgM, which was further enhanced by IL-6. The spontaneous secretion of IL-1 by neonatal splenocytes was below the detection limit, while adult splenocytes secreted 30.8 ± 5.2 U/ml, which is of the same order of magnitude as what was required to stimulate neonatal B cells to respond to TNP-Ficoll. Thus, the neonatal unresponsiveness to polysaccharide Ags could be due to the inability of a non-B cell population resident in the neonatal spleen to secrete sufficient quantities of IL-1.

Immunomodulatory effect of bovine lactoferrin pepsin hydrolysate on murine splenocytes and Peyer's patch cells

The effects were examined of a pepsin hydrolysate of bovine lactoferrin on the proliferation of murine splenocytes. The hydrolysate enhanced [3H]thymidine uptake by splenocytes, but undigested bovine lactoferrin exerted an inhibitory effect. The hydrolysate had the ability to inhibit the blastogenesis that was induced by mitogens such as concanavalin A, phytohemagglutinin, and lipopolysaccharide; inhibition was similar to that with undigested lactoferrin. These results suggested that the hydrolysate contained both immunostimulatory and immunoinhibitory peptides. The stimulatory effect of the hydrolysate in the absence of mitogens was then explored in more detail using nonadherent splenocytes. The proliferative response of splenocytes to the hydrolysate was much greater in the fraction that was enriched with B cells than in the fraction that was enriched with T cells. The hydrolysate did not affect thymocyte proliferation. These data indicated that the adherent cells resembling macrophages and found among the splenocytes were not the target cells of the hydrolysate. The stimulatory effect of the hydrolysate was due to the activation of B cells by the hydrolysate and enhanced immunoglobulin production by splenocytes. Because the hydrolysate also enhanced the proliferation and immunoglobulin A production of Peyer's Patch cells, the immunostimulatory effect of the hydrolysate in vivo was examined using mice that had been orally immunized with cholera toxin. The concentrations of immunoglobulin A conjugated against cholera toxin in bile and in the intestinal contents of mice fed liquid diets containing 1% (wt/vol) lactoferrin hydrolysate were greater than those of mice fed control diets. This result suggested that the use of the lactoferrin hydrolysate is beneficial to enhance mucosal immunity.

Effect of oral bacteria on peripheral blood leukocyte interleukin-6 and soluble interleukin-6 receptor production

To determine the effect of pathogenic oral bacteria on interleukin 6 (IL-6) and soluble IL-6 receptor production, we measured their release by human peripheral blood mononuclear cells in vitro. Unseparated peripheral blood mononuclear cells, peripheral blood lymphocytes (monocyte depleted), pure T cells, or monocytes were cultured with Actinobacillus actinomycetemcomitans, Capnocytophaga gingivalis, Capnocytophaga ochracea, Fusobacterium nucleatum or Porphyromonas gingivalis for 24 h. Supernatants were tested for IL-6 and soluble IL-6 receptor by enzyme-linked immunosorbent assay. Only monocytes and peripheral blood mononuclear cells responded with significant IL-6 release in the presence of all bacteria tested. However, peripheral blood lymphocytes were capable of producing IL-6 when activated by phytohemagglutinin or IL-2 followed by bacteria, though substantially less than cultures containing monocytes. No bacteria tested increased soluble IL-6 receptor release over spontaneous soluble IL-6 receptor release. We conclude that monocytes release IL-6 after contact with oral pathogens; however, soluble IL-6 receptor from T cells and monocytes is constitutively produced and may modulate IL-6 actions.

The effects of retinoic acid on immunoglobulin synthesis: role of interleukin 6

Retinoic acid (RA) and its parent compound, retinol (ROH, vitamin A), have been recognized as important immunopotentiating agents. Previous studies from our laboratory have demonstrated that RA can augment formalin-treated Staphylococcus aureus (SAC)-stimulated immunoglobulin (Ig) synthesis of cord blood mononuclear cells (CBMC). To determine the mechanism(s) by which RA modulates Ig synthesis, we studied the effects of RA on B cells and cytokine production. The addition of RA (10(-5) to 10(-10) M) to Epstein-Barr virus (EBV)-transformed B-cell clones derived from either adult or cord blood B cells augmented Ig secretion twofold. In contrast, cell proliferation was inhibited as measured by 3H-thymidine incorporation. We evaluated two cytokines known to be constitutively produced by EBV cell lines, IL-1 and IL-6. While RA had no effect on IL-1 production, IL-6 synthesis was greatly enhanced (20- to 45-fold), which was also reflected by an increase in steady-state mRNA levels for IL-6 but not TNF-alpha or TGF-beta on Northern blot analysis. Polyclonal rabbit anti-IL-6 antibodies were used to block the augmenting effects of RA on Ig synthesis of adenoidal B cells. RA-induced augmentation in IgG and IgA synthesis was blocked 58 and 29%, respectively, by anti-IL-6 antibodies. These studies suggest that the enhancing effects of RA on Ig synthesis are mediated, at least in part, by the autocrine or paracrine effects of IL-6 on B-cell differentiation.

Regulation of vascular endothelial growth factor expression in cultured keratinocytes. Implications for normal and impaired wound healing

Recent in situ hybridization studies had demonstrated a strong increase in vascular endothelial growth factor (VEGF) mRNA expression in the hyperproliferative epithelium during wound healing. To determine potential mediators of VEGF induction during this process, we analyzed the regulation of VEGF expression in cultured human keratinocytes. We found a large induction of VEGF expression upon treatment of quiescent cells with serum, epidermal growth factor, transforming growth factor-beta 1, keratinocyte growth factor, or the proinflammatory cytokine tumor necrosis factor alpha, respectively. Since all these factors are present at the wound site during the early phase of wound healing, they might also be responsible for VEGF induction after cutaneous injury. To determine the importance of increased VEGF production for wound repair, we compared the time course of VEGF mRNA expression during wound healing of healthy control mice with the kinetics of VEGF expression during skin repair of genetically diabetic db/db mice which are characterized by impaired wound healing. In normal mice we found elevated VEGF mRNA levels during the period when granulation tissue formation occurs. In contrast, VEGF mRNA levels even declined during this period in db/db mice, suggesting that a defect in VEGF regulation might be associated with wound healing disorders.

Demonstration of interleukin-2, interleukin-4 and interleukin-6 in sera from patients with localized scleroderma

Localized scleroderma has been reported to be accompanied by immunological abnormalities related to B cells, but little is known about T-cell activation in this disease. In this study, serum levels of interleukin-2 (IL-2), interleukin-4 (IL-4) and interleukin-6 (IL-6), which are known to be released by activated T cells, were determined using a sensitive enzyme-linked immunosorbent assay in 48 patients with localized scleroderma and 20 with systemic sclerosis, and in 20 healthy control subjects. IL-2, IL-4 and IL-6 were detected in serum from patients with localized scleroderma but not in that from healthy controls. The presence of antihistone antibodies correlated significantly with elevated IL-4 and IL-6 levels. Decreased serum levels of IL-2, IL-4 and IL-6 paralleled improvement in cutaneous sclerosis. Frequent detection of these lymphokines in serum from patients with localized scleroderma reflects T-cell activation in this disorder.

Acute effects of smoking and high experimental exposure to environmental tobacco smoke (ETS) on the immune system

Controversial results have been published on the immune response to cigarette smoking while the effects of exposure to environmental tobacco smoke (ETS) have not yet been reported. In a controlled study, acute effects of smoking and of a high environmental exposure to ETS on immunological parameters have been investigated. The study consisted of four experimental days, two control and two exposure days. On control days, 1 and 3, smokers (n = 5) and nonsmokers (n = 5) sat in an unventilated 45 m3 room for 8 h. On the exposure days, 2 and 4, each of the smokers smoked 24 cigarettes in 8 h, while the nonsmokers were exposed to the ETS generated by the smoking volunteers. Blood was drawn before and after each exposure session on all four experimental days for dosimetry of tobacco smoke exposure and determination of the immune response. Flow cytometry using monoclonal antibodies was used to determine CD3+ cells (whole T cells), CD19+ cells (B lymphocytes), CD16+ and CD56+ cells (natural killer cells), CD4+ cells (T-helper cells), CD8+ cells (T-suppressor cells), the CD4+/CD8+ (helper/suppressor ratio), and Fc receptors on granulocytes. Serum was analyzed for soluble CD14 receptors (sCD14), interleukin 1, interleukin 6 and prostaglandin E2 (PGE2). Functional stimulation assays were performed to determine the basal and induced level of reactive oxygen intermediate (ROI) production by polymorphic neutrophils. Exposure to tobacco smoke in both groups was confirmed by dosimetry of carboxyhemoglobin, plasma nicotine, and cotinine levels. In comparison to nonsmokers, smokers had elevated granulocyte cell counts, increased CD16+ and CD56+ cell levels and decreased CD3+ and CD19+ levels. Acute smoking, but not exposure to ETS, resulted in a slight decrease in the number of CD19+ cells and an increase in the number of granulocytes; the latter was restricted to one subject. Acute smoking and exposure to high experimental concentrations of ETS resulted in a slight increase in CD16+ and CD56+ cells. None of the changes determined in immunological parameters after either acute smoking or exposure to ETS reached statistical significance. Serum sCD14, cytokine and PGE2, functional stimulation of in vitro ROI production, and changes in Fc receptors were not affected by acute smoking or exposure to ETS. Although no clear guidelines exist to assess immunotoxicity in man, our data do not favor immunosuppression and the possibility of increased risk of infection in nonsmokers exposed to ETS under real-life conditions.

Cytomegalovirus and latency: an overview

Cytomegalovirus (CMV) is a member of the herpes virus group. Infection results in a variety of disorders which depend largely on the immune status of the host. A well known property of CMV is that after primary infection the virus persists in the body of the host resulting in latency. Severe immunodepression or immunodeficiency can cause reactivation of the virus from its latent state, leading to endogenous reinfection. In contrast to other herpes viruses, such as herpes simplex virus which persists in neurons, and Epstein Barr virus which persists in B lymphocytes, little is known about the localization of latent CMV. In order to obtain more insight in the organ or cell type serving as a reservoir for latent CMV, it is important to know more about the course of natural infection and the cells and organs involved. When more information is available about the localization of latent virus, studies concerning the physical state of viral DNA or the extent of viral transcription and/or translation will follow in the near future. In this review some properties of the epidemiology and transmission of human CMV, as well as data about acute infection will be given. In addition, some characteristics of the localization of latent CMV and the physical state of the virus will be discussed. Where necessary, particularly regarding insight into CMV-host interactions, knowledge of animal, particularly murine, rat and guinea pig CMV infections, will be discussed.

Interleukin-6 in synovial fluid is closely associated with chronic synovitis in rheumatoid arthritis

Interleukin-6 (IL-6) was detected at low levels in plasma [0.014 +/- 0.006 ng/ml (mean +/- SEM] and in high amounts in synovial fluid [SF; 2.6 +/- 2.2 ng/ml (mean +/- SEM)] of patients with rheumatoid arthritis. No correlation of IL-6 levels in plasma or SF with the ESR (n = 15) or with histological parameters of acute local synovitis (n = 10) was observed. In contrast, SF IL-6 was positively correlated with histological characteristics of chronic synovitis (n = 10; P < or = 0.01) and elevated plasma IgG concentrations (n = 15; P < or = 0.05). In vitro concentrations of IL-6 comparable to those detected in SF increased the production of both IgG and IgM by synovial membrane mononuclear cells. The present results contribute to the view that high local IL-6 concentrations in SF promote chronic synovitis in RA.

Interleukin-6, a new target for therapy in multiple myeloma?

During the past few years much insight has been gained into the immunobiology of multiple myeloma. It has become evident that the growth of myeloma cells is regulated by cytokines, notably interleukin-6. In this paper a brief review is given of the evidence derived from in vitro as well as in vivo observations that interleukin-6 is involved in the pathogenesis of multiple myeloma, and the implications of these findings for the development of new therapeutic strategies are discussed.

Cytokines, sepsis and immunomodulation

Tissue injury and infection produce significant alterations in host metabolic and immune homeostasis. It is increasingly clear that many of these changes result from a complex cascade of mononuclear phagocyte-derived endogenous mediators. Among the more important is a group of host proteins called cytokines, which play an integral role in mediating the host response to tissue injury and infection. Of these proteins, tumour necrosis factor (TNF) and interleukin (IL) types 1 and 6 have received much attention for their pathophysiological roles in infection and trauma. Evidence is reviewed for the involvement of these cytokines in the characteristic alterations in the metabolic and immune responses to such injury. These endogenous mediators initiate an integrated fuel substrate and hormonal adjustment to trauma and sepsis, and help to provide optimal metabolic homeostasis for systemic host defences. Widespread tissue injury, especially when associated with fulminant sepsis, may, however, precipitate massive release of TNF, IL-1 and IL-6, triggering a series of reactions involving multiple organs, and culminating in the 'sepsis syndrome'. New therapies designed to downregulate this aberrant response, either by neutralizing endotoxin directly or by blocking the release or actions of these cytokines, are reviewed. Although these treatments hold much promise for the future management of severely traumatized and infected patients, careful evaluation of both the benefits and complications of therapy is needed before widespread clinical use can be recommended.

Molecular and biological factors in the pathogenesis of ovarian cancer

BACKGROUND

The classic prognostic parameters are insufficient for predicting the prognosis of the individual patient. Knowledge of molecular and biological factors which are responsible for the development and progression of ovarian cancer may improve the prediction of prognosis.

MATERIALS AND METHODS

Recent data both on factors associated with the development and control of ovarian cancer cells and on DNA ploidy have been reviewed.

RESULTS

Observations suggest that steroid and peptide hormones have a role in disease etiology and progression, and that peptide growth factors and cytokines, oncogenes and tumor suppressor genes, by their impact on mitosis and cell number may influence the rate of mutations, which could confer malignant transformation. DNA ploidy is an objective independent prognostic factor. DNA aneuploidy indicates high risk, diploidy low risk. Only tumours shown to be DNA diploid by flow-cytometry and image cytometry are considered diploid. S-phase fraction is currently not reliable.

CONCLUSION

Understanding the mechanisms involved in ovarian cancer development and growth will allow opportunities for the rational design of effective anti-tumour treatment modalities. More objective and reproducible prognostic variables will improve the predictiveness of prognosis.

Spatial and temporal changes in compliance following implantation of bioresorbable vascular grafts

Compliance matching between the host vessel and vascular grafts used for small-diameter arterial replacements is thought to be important for long-term patency. However, currently available grafts elicit fibroplastic reactions, resulting in decreasing compliance with time after implantation. Bioresorbable prostheses elicit ingrowth of myofibroblasts containing abundant contractile elements. This led us to investigate whether compliance of implanted bioresorbable prostheses decreased as a function of time and if the kinetics of change correlated with the progression of tissue ingrowth. Woven polyglactin 910 prostheses (10 mm x 4 mm i.d.) were implanted into adult NZW rabbit infrarenal aortas and replicates were harvested serially through 8 months. Control grafts were implanted, and immediately resected. Dynamic compliance was measured at 1-mm axial increments along each explant using a pulse duplicator apparatus which exposed the harvested samples to realistic pulsatile hemodynamics. Compliance was calculated for proximal, mid, and distal segments of each graft and averaged at each time point by grouping into control (zero time, n = 3), early (1-4 weeks, n = 13), and late (6-36 weeks, n = 9) explant periods. At late explant periods both proximal and distal compliance were significantly greater than mid graft compliance (p < .02 and p < .03, respectively). There was a significant increase in proximal compliance between early and late explant times (p < .01). Measured increases in mid and distal segment compliance over time did not reach statistical significance. Myofibroblast laden tissue ingrowth into the inner capsule followed macrophage phagocytosis and was nearly complete prior to the time that an increase in compliance was demonstrated. Thus since the major histologic episodes precede the change in compliance, these are not likely initiated by this biomechanical change. We hypothesize the graft resorption coupled with the ingrowth of more compliant tissue likely leads to the increased compliance of the graft material.

Cytokines in tumour therapy

Cytokines are low molecular weight proteins released by cells of the immune system that have therapeutic potential in cancer. They include the interleukins, the interferons, tumour necrosis factor and the colony-stimulating factors. Cytokines are capable of producing significant and sustained responses against a number of tumours. Clinically, the highest response rates to cytokine immunotherapy have been seen in melanoma and renal cell cancer. Current efforts aim to reduce treatment-related toxicity while maintaining the efficacy of cytokines. The therapeutic potential of these agents may be increased with genetic manipulation by introducing genes encoding cytokines into tumour-infiltrating lymphocytes and certain tumour cells. However, immunotherapy remains time consuming and expensive, and further developments are necessary before it can have a definitive role in tumour management.

Macrophage response to bacteria: induction of marked secretory and cellular activities by lipoteichoic acids

Lipoteichoic acids (LTAs) from various bacterial species, including Staphylococcus aureus, Streptococcus pyogenes, Streptococcus pneumoniae, Enterococcus faecalis, and Listeria monocytogenes, were examined for the ability to induce secretory and cellular responses in a pure population of bone marrow-derived mononuclear phagocytes. Some of the highly purified LTAs, in particular LTAs from Bacillus subtilis, S. pyogenes, E. faecalis, and Enterococcus hirae, were able to affect each of the macrophage parameters measured, i.e., reductive capacity, secretion of tumor necrosis factor and nitrite, and tumoricidal activity. As after stimulation with whole organisms or other bacterial products, secretion of tumor necrosis factor induced by these LTAs reached its maximum within the first few hours of the interaction, while secretion of nitrite and tumoricidal activity required 24 to 36 h for full expression. Other purified LTAs, i.e., LTAs from Streptococcus sanguis, S. pneumoniae, and L. monocytogenes, as well as lipomannan from Micrococcus luteus affected only some of these parameters, while native LTA from S. aureus was inactive. There was no obvious correlation between biological activity and chain length, kind of glycosyl substituents, glycolipid structures, or fatty acid composition of LTAs. Deacylation of LTAs resulted in a complete loss of activity, and deacylated LTAs did not impair the activity of their acylated counterparts, suggesting that acyl chains may be essential for binding of LTA to the cell surface. The results demonstrate that some LTA species are potent inducers of macrophage secretory and cellular activities.

Characterization of a novel cell line from pleomorphic adenoma of the parotid gland with myoepithelial phenotype and producing interleukin-6 as an autocrine growth factor

A cell line was obtained from a primary culture of a pleomorphic adenoma of the parotid gland in a 24-year-old woman. The cells of the line (PA 16/23) grew spontaneously in minimal culture conditions and showed stable morphologic characteristics over 30 passages. PA 16/23 cells had immunophenotypic and ultrastructural features similar to those of transformed myoepithelial cells, which are regarded as the precursors of pleomorphic adenomas. Furthermore, these cells have been demonstrated immunocytochemically to contain interleukin-6 (IL-6) on light and electron microscopic examination. IL-6 also has been found by enzyme-linked immunosorbent assay in the culture supernatant and has been proven to be capable of stimulating growth of the PA 16/23 cells.

Factor(s) required by EBV transformed lymphocytes to grow under limiting dilution conditions

IL-6 was demonstrated to promote growth of EBV transformed lymphocytes. However IL-6 was ineffective at promoting growth of EBV transformed lymphocytes cultured at the single cell level under limiting dilution conditions. On the contrary, HECS, which is known to contain IL-6, supported very efficiently the growth of 1-2 EBV transformed cells. When IL-6 was removed from HECS, by using specific antibodies, no reduction in HECS activity was observed, indicating that probably more than one growth factor is required to support the growth of EBV transformed cells cultured at very low cell numbers in the absence of feeder cells.