Interleukin-10 inhibits apoptotic cell death in infectious mononucleosis T cells

Impact of Hepatitis C Virus Infection of Peripheral Blood Mononuclear Cells on the Immune System

Hepatitis C is a worldwide liver disease caused by hepatitis C virus (HCV) infection. The virus causes acute and chronic liver inflammation, and it is transmitted mainly by exposure to contaminated blood. HCV is capable of infecting hepatocytes and peripheral blood mononuclear cells, causing complications and disease progression. This mini review provides an overview of HCV infection, including details on the virological aspects, infection of the immune cells, and its impact on the immune system.

Transplantation of CRISPRa system engineered IL10-overexpressing bone marrow-derived mesenchymal stem cells for the treatment of myocardial infarction in diabetic mice

Background

Myocardial infarction (MI) is a common cause of mortality in people. Mesenchymal stem cell (MSC) has been shown to exert therapeutic potential to treat myocardial infarction (MI). However, in patients with diabetes, the diabetic environment affected MSCs activity and could impair the efficacy of treatment. Interleukin-10 (IL-10) has been shown to attenuate MI by suppressing inflammation. In current study, the combination of MSC transplantation with IL-10 was evaluated in a diabetic mice model with MI.

Methods

We engineered bone marrow derived MSCs (BM-MSCs) to overexpress IL-10 by using CRISPR activation. We established the diabetic mice model with MI and monitored the IL-10 expression after BM-MSCs transplantation. We also evaluated the effects of BM-MSCs transplantation on inflammatory response, cell apoptosis, cardiac function and angiogenesis.

Results

CRISPR activation system enabled overexpression of IL-10 in BM-MSCs. Transplantation of BM-MSCs overexpressing IL-10 resulted in IL-10 expression in heart after transplantation. Transplantation of BM-MSCs overexpressing IL-10 inhibited inflammatory cell infiltration and pro-inflammatory cytokines production, improved cardiac functional recovery, alleviated cardiac injury, decreased apoptosis of cardiac cells and increased angiogenesis.

Conclusion

In summary, we have demonstrated the therapeutic potential of IL-10 overexpressed BM-MSCs in the treatment of MI in diabetic mice.

Increased Spontaneous Programmed Cell Death Is Associated with Impaired Cytokine Secretion in Peripheral Blood Mononuclear Cells from Hepatitis C Virus-Positive Patients

Peripheral blood mononuclear cells (PBMCs) play a critical role in clearing hepatitis C virus (HCV). PBMC defects have been linked with HCV infection; however, the underlying mechanisms remain obscure. We hypothesized that PBMCs of HCV-infected patients are more susceptible to programmed cell death (PCD), and are therefore unable to clear HCV. We compared spontaneous PBMC PCD and cytokine [interleukin (IL)-1, -6, -8, -10, and -12] secretion between untreated (naive) HCV⁺ and treated [sustained responder (SR)] patients with HCV, and HCV^- healthy controls. Spontaneous PBMC PCD was assessed by annexin-V fluorescein isothiocyanate/propidium iodide staining, and cytokine levels were measured by cytometric bead array. Differences between groups were analyzed through paired and nonpaired t tests and Mann-Whitney U test. The rate of spontaneous PCD was higher in PBMCs of naive HCV⁺ patients (p < 0.0001) and SR-HCV patients (p < 0.002) than in HCV^- controls. Significantly low levels of IL-8, -6, and -10 were detected in the supernatant of cell cultures of PBMCs from naive HCV⁺ (p < 0.05) and SR-HCV (p < 0.05) patients relative to HCV^- controls. There was no difference between the naive HCV⁺ and SR-HCV groups in terms of PBMC PCD rate or cytokine levels. The present findings indicate that HCV infection is associated with increased PBMC susceptibility to PCD and decreased production of IL-8, -6, and -10.

IL-10 is required for polarization of macrophages to M2-like phenotype by mycobacterial DnaK (heat shock protein 70)

Macrophages are key cells in the innate immune system. They phagocytose pathogens and cellular debris, promote inflammation, and have important roles in tumor immunity. Depending on the microenvironment, macrophages can polarize to M1 (inflammatory) or M2 (anti-inflammatory) phenotypes. Extracellular DnaK (the bacterial ortholog of the mammalian Hsp70) from Mycobacterium tuberculosis (Mtb) was described to exert immune modulatory roles in an IL-10 dependent manner. We have previously observed that endotoxin-free DnaK can polarize macrophages to an M2-like phenotype. However, the mechanisms that underlie this polarization need to be further investigated. IL-10 has been described to promote macrophage polarization, so we investigated the involvement of this cytokine in macrophages stimulated with extracellular DnaK. IL-10 was required to induce the expression of M2 markers - Ym1 and Fizz, when macrophages were treated with DnaK. Blockade of IL-10R also impaired DnaK induced polarization, demonstrating the requirement of the IL-10/IL-10R signaling pathway in this polarization. DnaK was able to induce TGF-β mRNA in treated macrophages in an IL-10 dependent manner. However, protein TGF-β could not be detected in culture supernatants. Finally, using an in vivo allogeneic melanoma model, we observed that DnaK-treated macrophages can promote tumor growth in an IL-10-dependent manner. Our results indicate that the IL-10/IL-10R axis is required for DnaK-induced M2-like polarization in murine macrophages.

Complexity and Controversies over the Cytokine Profiles of T Helper Cell Subpopulations in Tuberculosis

Tuberculosis (TB) is a contagious infectious disease caused by the TB-causing bacillus Mycobacterium tuberculosis and is considered a public health problem with enormous social impact. Disease progression is determined mainly by the balance between the microorganism and the host defense systems. Although the immune system controls the infection, this control does not necessarily lead to sterilization. Over recent decades, the patterns of CD4+ T cell responses have been studied with a goal of complete understanding of the immunological mechanisms involved in the maintenance of latent or active tuberculosis infection and of the clinical cure after treatment. Conflicting results have been suggested over the years, particularly in studies comparing experimental models and human disease. In recent years, in addition to Th1, Th2, and Th17 profiles, new standards of cellular immune responses, such as Th9, Th22, and IFN-γ-IL-10 double-producing Th cells, discussed here, have also been described. Additionally, many new roles and cellular sources have been described for IL-10, demonstrating a critical role for this cytokine as regulatory, rather than merely pathogenic cytokine, involved in the establishment of chronic latent infection, in the clinical cure after treatment and in keeping antibacillary effector mechanisms active to prevent immune-mediated damage.

Challenges and future perspectives of T cell immunotherapy in cancer

Since the formulation of the tumour immunosurveillance theory, considerable focus has been on enhancing the effectiveness of host antitumour immunity, particularly with respect to T cells. A cancer evades or alters the host immune response by various ways to ensure its development and survival. These include modifications of the immune cell metabolism and T cell signalling. An inhibitory cytokine milieu in the tumour microenvironment also leads to immune suppression and tumour progression within a host. This review traces the development in the field and attempts to summarize the hurdles that the approach of adoptive T cell immunotherapy against cancer faces, and discusses the conditions that must be improved to allow effective eradication of cancer.

Characterization of CD4⁺ T-cell immune activation and interleukin 10 levels among HIV, hepatitis C virus, and HIV/HCV-coinfected patients

BACKGROUND

HIV/hepatitis C virus (HCV)-coinfected patients have accelerated liver disease compared with HCV monoinfection. In HIV-positive patients with viral suppression, data comparing inflammatory cytokines and immune activation between HIV/HCV coinfection with chronic hepatitis C (CHC) to HIV/HCV-seropositive patients with cleared HCV are limited.

METHODS

Fifty-nine age- and sex-matched patients were stratified: (1) HIV monoinfection (n = 15); (2) HCV monoinfection with CHC (n = 15); (3) HIV/HCV coinfection with CHC (n = 14); and (4) HIV/HCV seropositive with cleared HCV (n = 15). All HIV-positive patients had undetectable HIV viremia, and median CD4 was 420 cells per microliter. Liver fibrosis was assessed in each subject using transient elastography. Cells were collected for CD4 and CD8 immune activation (CD38/HLA-DR) markers via flow cytometry and plasma for luminex-multiplex cytokine assays.

RESULTS

CD38⁺HLA-DR⁺ expression on CD4⁺ T cells was significantly increased in HIV/HCV coinfection with CHC (7%) versus HCV monoinfection (4%) (P = 0.012). CD4⁺ total HLA-DR⁺ expression was significantly increased in HIV/HCV coinfection with CHC (43%) versus HIV monoinfection (31%) (P = 0.010) and HIV/HCV seropositive with cleared HCV (38%) (P = 0.046). Total CD4⁺CD38⁺ and CD4⁺CD38⁺HLA-DR⁻ expression was significantly higher in HIV monoinfection (23% and 18%) than HCV moninfection (13%, P = 0.002% and 9%, P = 0.001, respectively). Interleukin 10 levels were significantly lower in HIV monoinfection versus HIV/HCV coinfection with CHC (P = 0.0002). In multivariate analysis, severe fibrosis was associated with lower expression of CD4⁺CD38⁺HLA-DR⁺ and CD4⁺ total CD38⁺ than mild-moderate fibrosis (P = 0.03 and 0.03, respectively).

CONCLUSIONS

CD4 immune activation with HLA-DR⁺ expression in HIV/HCV coinfection with well-controlled HIV may arise from chronic HCV viremia. Conversely, CD4⁺CD38⁺ expression may be driven by underlying HIV infection. CD4 immune activation was unexpectedly found to be associated with decreased liver fibrosis.

Chemokine programming dendritic cell antigen response: part II - programming antigen presentation to T lymphocytes by partially maintaining immature dendritic cell phenotype

In a companion article to this study,(1) the successful programming of a JAWSII dendritic cell (DC) line's antigen uptake and processing was demonstrated based on pre-treatment of DCs with a specific 'cocktail' of select chemokines. Chemokine pre-treatment modulated cytokine production before and after DC maturation [by lipopolysaccharide (LPS)]. After DC maturation, it induced an antigen uptake and processing capacity at levels 36% and 82% higher than in immature DCs, respectively. Such programming proffers a potential new approach to enhance vaccine efficiency. Unfortunately, simply enhancing antigen uptake does not guarantee the desired activation and proliferation of lymphocytes, e.g. CD4(+) T cells. In this study, phenotype changes and antigen presentation capacity of chemokine pre-treated murine bone marrow-derived DCs were examined in long-term co-culture with antigen-specific CD4(+) T cells to quantify how chemokine pre-treatment may impact the adaptive immune response. When a model antigen, ovalbumin (OVA), was added after intentional LPS maturation of chemokine-treated DCs, OVA-biased CD4(+) T-cell proliferation was initiated from ~ 100% more undivided naive T cells as compared to DCs treated only with LPS. Secretion of the cytokines interferon-γ, interleukin-1β, interleukin-2 and interleukin-10 in the CD4(+) T cell : DC co-culture (with or without chemokine pre-treatment) were essentially the same. Chemokine programming of DCs with a 7 : 3 ratio of CCL3 : CCL19 followed by LPS treatment maintained partial immature phenotypes of DCs, as indicated by surface marker (CD80 and CD86) expression over time. Results here and in our companion paper suggest that chemokine programming of DCs may provide a novel immunotherapy strategy to obviate the natural endocytosis limit of DC antigen uptake, thus potentially increasing DC-based vaccine efficiency.

Interleukin 10 responses are associated with sustained CD4 T-cell counts in treated HIV infection

BACKGROUND

Inflammation persists in treated human immunodeficiency virus (HIV) infection and may contribute to an increased risk for non-AIDS-related pathologies. We investigated the correlation of cytokine responses with changes in CD4 T-cell levels and coinfection with hepatitis C virus (HCV) during highly active antiretroviral treatment (HAART).

METHODS

A total of 383 participants in the Women's Interagency HIV Study (212 with HIV monoinfection, 56 with HCV monoinfection, and 115 with HIV/HCV coinfection) were studied. HIV-infected women had <1000 HIV RNA copies/mL, 99.7% had >200 CD4 T cells/μL; 98% were receiving HAART at baseline. Changes in CD4 T-cell count between baseline and 2-4 years later were calculated. Peripheral blood mononuclear cells (PBMCs) obtained at baseline were used to measure interleukin 1β (IL-1β), interleukin 6 (IL-6), interleukin 10 (IL-10), interleukin 12 (IL-12), and tumor necrosis factor α (TNF-α) responses to Toll-like receptor (TLR) 3 and TLR4 stimulation.

RESULTS

Undetectable HIV RNA (<80 copies/mL) at baseline and secretion of IL-10 by PBMCs were positively associated with gains in CD4 T-cell counts at follow-up. Inflammatory cytokines (IL-1β, IL-6, IL-12, and TNF-α) were also produced in TLR-stimulated cultures, but only IL-10 was significantly associated with sustained increases in CD4 T-cell levels. This association was significant only in women with HIV monoinfection, indicating that HCV coinfection is an important factor limiting gains in CD4 T-cell counts, possibly by contributing to unbalanced persistent inflammation.

CONCLUSIONS

Secreted IL-10 from PBMCs may balance the inflammatory environment of HIV, resulting in CD4 T-cell stability.

In vivo cytokine modulatory effects of cinnamaldehyde, the major constituent of leaf essential oil from Cinnamomum osmophloeum Kaneh

The purpose of this study was to analyse the major compound in the leaf essential oil of Cinnamomum osmophloeum Kaneh. and to examine its in vivo toxicity and cytokine-modulatory effects. The HS-GC/MS and quantitative HPLC analyses showed the concentrations of the major compounds, cinnamaldehyde, benzaldehyde and 3-phenylpropionaldehyde, in the leaf essential oil of Cinnamomum osmophloeum to be 16.88, 1.28 and 1.70 mg/mL, respectively. Acute and sub-acute toxicity tests identified no significant changes in body weight, liver and kidney function indices, and pathology for the mice treated with up to 1 mL/kg body weight of Cinnamomum osmophloeum leaf essential oil or up to 4 mg/kg body weight of cinnamaldehyde. A murine model was established using ovalbumin (OVA)-primed Balb/C mice treated with various concentrations of Cinnamomum osmophloeum leaf essential oil or cinnamaldehyde daily for 4 weeks. The results of tests with commercial ELISA kits indicated no significant cytokine-modulatory effects in mice treated with Cinnamomum osmophloeum leaf essential oil; however, the serum concentrations of IL-2, IL-4 and IL-10, but not IFN-γ, significantly increased in animals treated with 1 mg/kg body weight of cinnamaldehyde during the 4-week period. The possibility that the other constituents act as antagonists of cinnamaldehyde cannot be excluded.

Aberrant tissue localization of fungus-specific CD4+ T cells in IL-10-deficient mice

Aspergillus fumigatus, a common environmental fungus, can cause lethal invasive infections in immunocompromised hosts. In immunocompetent individuals, however, inhaled A. fumigatus spores prime CD4(+) T cells and activate immune responses that prevent invasive infection. Calibration of inflammatory responses to levels that prevent fungal invasion without inducing collateral tissue damage is essential for host survival, but the underlying regulatory mechanisms remain undefined. Although IL-10 is a validated regulatory cytokine that suppresses immune responses, and IL-10 deficiency or blockade generally enhances immune responses, we find that A. fumigatus-specific T cell frequencies are markedly reduced in airways of IL-10-deficient mice. T cell priming, proliferation, and survival were unaffected by IL-10 deficiency and did not account for decreased frequencies of A. fumigatus-specific T cells in the airways of IL-10-deficient mice. Instead, IL-10 deficiency results in redistribution of A. fumigatus-specific T cells from infected lungs to the gut, a process that is reversed by antibiotic-mediated depletion of intestinal microbes. Our studies demonstrate that disregulated immune responses in the gut can result in dramatic redistribution of pathogen-specific T cells within the host.

Pathogen-Specific CD8 T Cell Responses Are Directly Inhibited by IL-10

Regulation of CD8 T cell expansion and contraction is essential for successful immune defense against intracellular pathogens. IL-10 is a regulatory cytokine that can restrict T cell responses by inhibiting APC functions. IL-10, however, can also have direct effects on T cells. Although blockade or genetic deletion of IL-10 enhances T cell-mediated resistance to infections, the extent to which IL-10 limits in vivo APC function or T cell activation/proliferation remains unknown. Herein, we demonstrate that primary and memory CD8 T cell responses following Listeria monocytogenes infection are enhanced by the absence of IL-10. Surface expression of the IL-10R is transiently up-regulated on CD8 T cells following activation, suggesting that activated T cells can respond to IL-10 directly. Consistent with this notion, CD8 T cells lacking IL-10R2 underwent greater expansion than wild-type T cells upon L. monocytogenes infection. The absence of IL-10R2 on APCs, in contrast, did not enhance T cell responses following infection. Our studies demonstrate that IL-10 produced during bacterial infection directly limits expansion of pathogen-specific CD8 T cells and reveal an extrinsic regulatory mechanism that modulates the magnitude of memory T cell responses.

Phenotypic changes induced by IL-12 priming regulate effector and memory CD8 T cell differentiation

In addition to TCR and co-stimulatory signals, inflammatory cytokines such as IL-12 provide important signals for differentiation and survival of activated CD8 T cells. In the present study, to investigate the mechanisms by which IL-12 priming contributes to activation and enhanced survival of CD8 T cells, we searched the differentially regulated genes and markers by IL-12 during antigenic stimulation. Here, we show that IL-12 priming results in the increased subpopulation of CD127(hi) cells, which differentiates into long-lived memory cells. We also found that IL-12 priming induces IL-10 expression from activated CD8 T cells, which is distinct from CD127 up-regulation. Direct IL-10 priming of CD8 T cells results in the significant increase of effector and memory CD8 T cell population after adoptive transfer, and this priming effect is closely associated with less susceptibility to apoptosis. Although IL-10 is known as a cytokine with anti-inflammatory and immunosuppressive properties, our results have shown that IL-10 has a direct and positive effect on the survival of CD8 T cells. Together, we suggest that IL-10-dependent and independent effects of IL-12 play important roles in regulating differentiation and survival of activated CD8 T cells into effector and memory cells.

Intestinal Fibroblast-Derived IL-10 Increases Survival of Mucosal T Cells by Inhibiting Growth Factor Deprivation- and Fas-Mediated Apoptosis

Mucosal T cells are essential to immune tolerance in the intestine, an organ constantly exposed to large amounts of dietary and bacterial Ags. We investigated whether local fibroblasts affect mucosal T cell survival, which is critical for maintenance of immune tolerance. Coculture with autologous fibroblasts significantly increased viability of mucosal T cells by inhibiting IL-2 deprivation- and Fas-mediated apoptosis, an effect that was both contact- and secreted product-dependent. Investigation of anti-apoptotic factors in the fibroblast-conditioned medium (FCM) revealed the presence of IL-10 and PGE2, but not IFN-beta, IL-2, or IL-15. Although recombinant IFN-beta, but not PGE2, effectively prevented T cell apoptosis, neutralizing Ab studies showed that only IL-10 blockade significantly increased T cells apoptosis, whereas neutralizing IFN-beta or IFN-alpha failed to inhibit the anti-apoptotic effect of FCM. To confirm that fibroblast-derived IL-10 was responsible for preserving mucosal T cell viability, IL-10 mRNA was demonstrated in fibroblasts by Southern blotting and RT-PCR. When FCM was submitted to HPLC fractionation, only the peak matching rIL-10 contained the anti-apoptotic activity, and this was eliminated by treatment with an IL-10-neutralizing Ab. Finally, when fibroblasts were transiently transfected with IL-10 antisense oligonucleotides, the conditioned medium lost its T cell anti-apoptotic effect, whereas medium from fibroblasts transfected with IFN-beta antisense oligonucleotides displayed the same anti-apoptotic activity of medium from untransfected fibroblasts. These results indicate that local fibroblast-derived IL-10 is critically involved in the survival of mucosal T cells, underscoring the crucial importance of studying organ-specific cells and products to define the mechanisms of immune homeostasis in specialized tissue microenvironments like the intestinal mucosa.

Priming in the presence of IL-10 results in direct enhancement of CD8+ T cell primary responses and inhibition of secondary responses

Although IL-10 acts as an inhibitory cytokine for APC and CD4(+) T cell function, its effects on CD8(+) T cells are unclear. Additionally, little is known about whether initial priming in the presence of IL-10 can have long-lasting effects and influence subsequent CD8(+) T cell responses that occur in the absence of the cytokine. In the present study, we clarified the role of IL-10 during primary responses and examined whether exposure to IL-10 during initial priming of CD8(+) T cells impacted secondary responses. To determine the effect of IL-10 on Ag-specific T cell responses, peptide-pulsed IL-10R2(-/-) splenic dendritic cells were used to prime T cells from OT-I CD8(+) TCR transgenic mice. During the primary response, the presence of IL-10 resulted in enhancement of CD8(+) T cell numbers without detectable alterations in the kinetics or percentage of cells that underwent proliferation. A modest increase in survival, not attributable to Bcl-2 or Bcl-x(L), was also observed with IL-10 treatment. Other parameters of CD8(+) T cell function, including IL-2, IFN-gamma, TNF-alpha, and granzyme production, were unaltered. In contrast, initial exposure to IL-10 during the primary response resulted in decreased OT-I expansion during secondary stimulation. This was accompanied by lowered IL-2 levels and reduced percentages of proliferating BrdU(+) cells and OT-I cells that were CD25(high). IFN-gamma, TNF-alpha, and granzyme production were unaltered. These data suggest that initial exposure of CD8(+) T cells to IL-10 may be temporarily stimulatory; however, programming of the cells may be altered, resulting in diminished overall responses.

Semiquantitative Detection of Cytokine Messages in X-Irradiated and Regenerating Rat Thymus

We investigated the expression of cytokine mRNA derived from thymocytes or thymic epithelial cells in X-irradiated (8 Gy) and recovering rat thymuses, according to our previous observation (Mizutani et al., Radiat. Res. 157, 281-289, 2002). The changes in mRNA expression level of interleukin 2 (Il2), Il4, tumor necrosis factor alpha (Tnf), interferon gamma (Ifng), and transforming growth factor beta (Tgfb) were examined. The mRNA expression of Il2 and Il4 decreased from day 5 to day 14 after irradiation. Thereafter, the expression level of Il2 mRNA recovered to normal control levels; however, the expression of Il4 mRNA tended toward significantly low levels. Tnf mRNA expression decreased on day 5 after irradiation and then showed a gradual increase back to normal control levels. Tgfb mRNA expression did not change significantly. Ifng mRNA expression was transiently enhanced from day 11 to day 14. The mRNA expression levels of Il10 increased significantly from day 3 to day 7 after irradiation. In addition, the mRNA expression of thymic epithelial cell-derived Il7 showed a transient decrease on day 3; however, then it showed a continuous increase from day 5 to day 21, finally reaching twice the normal control levels after X irradiation. These observations suggest that the expression of cytokine messages in the irradiated thymus changed significantly and did not return to normal for a long time after 8 Gy irradiation.

Modulation of Fas-dependent apoptosis: a dynamic process controlling both the persistence and death of CD4 regulatory T cells and effector T cells

We have previously shown that regulatory CD25(+)CD4(+) T cells are resistant to clonal deletion induced by viral superantigen in vivo. In this work we report that isolated CD25(+)CD4(+) T cells activated in vitro by anti-CD3 Ab are resistant to Fas-induced apoptosis, in contrast to their CD25(-)CD4(+) counterparts. Resistance of CD25(+)CD4(+) T cells to Fas-dependent activation-induced cell death is not linked to their inability to produce IL-2 or to their ability to produce IL-10. The sensitivity of both populations to Fas-induced apoptosis can be modulated in vitro by changing the CD25(+)CD4(+):CD25(-)CD4(+) T cell ratio. The sensitivity of CD25(-)CD4(+) T cells to apoptosis can be reduced, while the sensitivity of CD25(+)CD4(+) T cells can be enhanced. Modulation of Fas-dependent apoptosis is associated with changes in cytokine production. However, while CD25(-)CD4(+) T cell apoptosis is highly dependent on IL-2 (production of which is inhibited by CD25(+)CD4(+) T cells in coculture), modulation of CD25(+)CD4(+) T cell apoptosis is IL-2 independent. Taken together, these results suggest that CD25(+)CD4(+) and CD25(-)CD4(+) T cell sensitivity to Fas-dependent apoptosis is dynamically modulated during immune responses; this modulation appears to help maintain a permanent population of regulatory T cells required to control effector T cells.

Expansion of a CD28-intermediate subset among CD8 T cells in patients with infectious mononucleosis

Infectious mononucleosis (IM) is an acute sporadic infection that usually affects young adults, and during infection a massive expansion of CD8 T cells is generally considered to occur. However, CD28 expression of the expanded cells has not been characterized. When peripheral blood mononuclear cells of acute IM (AIM) patients were analyzed by flow cytometry, a continuous spectrum of CD28 intensity ranging from negative to high, which could be separated into CD28 negative, intermediate (int), and positive, was seen for CD8 T cells. We studied 26 IM patients who were diagnosed on the basis of standard methods and found that all patients had the continuous CD28 spectrum. CD28 is a costimulatory molecule on T cells, and its expression is associated with the subdivision of CD8 cells into cytotoxic (CD28-positive) and suppressor (CD28-negative) T cells. After 24 h of ex vivo culturing, however, the continuous spectrum was found to consist of only CD28-positive and CD28-negative CD8 T cells, because the CD28-int cells had disappeared due to apoptosis. The CD28-int T cells have several cytotoxic functions, suggesting that CD28-int T cells are effectors. Examination of other costimulatory markers in AIM patients showed that CD80 and CD152 were not affected. In patients with other viral infections, such as measles or rubella, however, the continuous spectrum was not detected. These results suggest that there is an unusual CD28 expression pattern in patients with AIM, namely, the presence of a functional CD28-int subset among CD8 T cells. These findings are of special importance for clarifying the defense mechanism against Epstein-Barr virus infection, and the role of CD28 molecules in humans and should also be helpful for the diagnosis of AIM.

Targeting the host inflammatory response in traumatic spinal cord injury

Both acute and chronic inflammatory processes have been shown to influence outcome in experimental models of spinal cord injury. Although early inflammatory responses may participate in secondary injury processes, more delayed inflammatory events may be reparative. Therapeutic strategies that target these events are currently based on experimental findings that have clarified the cellular and molecular processes involved in the inflammatory response to injury. An increasing body of literature supports the hypothesis that acute inflammatory events are attenuated by therapeutic hypothermia and other anti-inflammatory strategies, whereas immune neuroprotection and axonal regeneration can be achieved by transfer of activated T cells or by treatment with therapeutic vaccines. These data are summarized in the present review.

Inflammatory and anti-inflammatory cytokines regulate the recovery from sublethal X irradiation in rat thymus

We investigated the regeneration of rat thymus after sublethal X irradiation (6 Gy). The number of thymocytes was much lower on day 3 after irradiation, and many apoptotic cells were observed. However, by day 5, there had been a rapid proliferation of thymocytes. Since cytokines are considered to be important regulatory factors in postirradiation recovery, we performed in vivo cytokine assays using semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) and found serial changes in the cytokine message. The messenger RNA (mRNA) expression of the pro-inflammatory cytokines interleukin 1 beta (Il1b), Il6 and tumor necrosis factor alpha (Tnf) was higher than normal on day 3, lower on day 5, and higher again on day 7. In particular, Tnf was completely absent on day 5 and was expressed again on day 7. Of the anti-inflammatory cytokines Il4, transforming growth factor beta (Tgfb) and Il10, only the Il10 message changed substantially. Il10 expression was very high on day 5 but was completely absent on day 7. Thus the Tnf and Il10 messages were expressed alternately. The changes in the distribution of macrophages detected by the immunohistochemical analysis may be related to the changes in the cytokines. Analysis of cytokine messages in the regenerating thymus in vivo may provide new insights into potential therapies for radiation-induced damage.

Catalase contents in cells determine sensitivity to the apoptosis inducer gallic acid

Gallic acid (3,4,5-trihydroxybenzoic acid, GA) is known to induce apoptosis in cancer cells at lower IC50 values compared with values for normal cells. Apoptosis is inhibited completely by the addition of conditioned medium from cultured hepatocytes, whereas it is not prevented by conditioned media from tumor cells. We therefore studied the reason for the different response to GA-induced apoposis. GA-induced dRLh-84 cell death was completely abolished by the addition of peroxisome or cytosol as well as conditioned medium from primary cultured rat hepatocyte. As GA-induced cell death is known to be mediated by reactive oxygen species (ROS) and intracellular Ca2+, we determined the type of ROS generated by GA and found that GA generated hydrogen peroxide in culture medium. The addition of hydrogen peroxide generated by GA induced cell death in dRLh-84 cells. These results suggest that GA-induced cell death is mediated by hydrogen peroxide. On the other hand, the inhibitory activity of hepatocyte medium on GA-induced cell death was completely abolished by anti-catalase antibody. When the amount of catalase antigen was determined by Western blotting analysis, conditioned medium and the cytoplasm of hepatocytes contained high concentrations of catalase. Conditioned media from various tumor cell lines did not contain catalase, and the cytoplasm contained only low levels of catalase. These results show that GA-sensitive cells, including various tumor cells, produce only small amounts of catalase and secreted little enzyme into media, suggesting a lack of protective machinery against GA. In contrast, GA-insensitive cells, including hepatocytes, produce large amounts of catalase and release it in medium, resulting in the development of insensitivity to GA. In conclusion, catalase contents in cells determine different sensitivity to GA.

Susceptibility to cytomegalovirus infection may be dependent on the cytokine response to the virus

BACKGROUND

Cytomegalovirus (CMV) infection is an important cause of morbidity and mortality in an immunocompromised host. Pulmonary infection with CMV results in an inflammatory response, which includes the local production of cytokines. Cytokine production stimulated by CMV infection serves to activate a series of immunologic responses involved in viral clearance. Previous work has demonstrated that different mouse strains express variable sensitivity to CMV infection.

METHODS

Using mouse strains that express sensitive (BALB/cj) and resistant (C57BL/6) CMV phenotypes, we asked whether the differences in susceptibility to infection were caused by differences in pulmonary cytokine production after intraperitoneal infection with CMV.

RESULTS

C57 mice demonstrated a higher total bronchoalveolar lavage (BAL) and BAL lymphocyte count at 3 and 7 days after intraperitoneal infection compared with BALB mice. There were no differences in BAL cytokine production; however, we were able to demonstrate differences in CMV DNA load in the lungs of BALB mice compared with that of C57 mice. In addition, there appeared to be increased whole-lung production of the TH2 cytokine IL-10 in the BALB mice versus the C57 mice.

CONCLUSIONS

This observation suggests that the genetic susceptibility to CMV infection may, in part, be regulated by differences in cytokines production within the local environment.

Natural regulatory CD4 T cells expressing CD25

In normal mice, a subpopulation of CD4 T cells constitutively express CD25. These cells behave as regulatory T cells in autoimmune and inflammatory reactions, in tolerance to superantigens, and in peripheral T-cell homeostasis. They are unable to produce interleukin (IL)-2, and are dependent on IL-2 for growth in vitro and in vivo. CD4 CD25(+) T cells spontaneously secrete IL-10, which is involved in some of their regulatory functions. They are resistant to apoptosis, but can be tolerized by anergy.

Diagnosis of atypical cases of infectious mononucleosis

The variable manifestations of infectious mononucleosis rarely cause clinicians to suspect primary Epstein-Barr virus or cytomegalovirus infection; consequently, costly diagnostic tests and unnecessary treatments are undertaken. Seventeen cases of clinically atypical and 11 cases of clinically typical infectious mononucleosis were diagnosed through screening for atypical and apoptotic lymphocytes in the peripheral blood samples by means of an automated hematologic analyzer. Atypical and typical cases did not differ significantly with respect to peripheral white blood cell counts; percentages of lymphocytes, atypical lymphocytes, CD4(+) lymphocytes, human leukocyte antigen--DR positivity in CD3 lymphocytes, or apoptotic cells in blood smear after incubation; or levels of aspartate aminotransferase, alanine aminotransferase, and lactate dehydrogenase. Only the percentage of CD8(+) lymphocytes was significantly higher in patients with typical infectious mononucleosis than it was in patients with atypical infectious mononucleosis. Because certain atypical cases of infectious mononucleosis display laboratory abnormalities that are characteristic of typical infectious mononucleosis, enhanced awareness can help in the diagnosis.

Interleukin 10 modulation of tumour necrosis factor receptors requires tyrosine kinases but not the PI 3-kinase/p70 S6 kinase pathway

We have previously shown that interleukin (IL-)10-induced proliferation of the murine mast cell line D36, was dependent upon the activation of PI 3-kinase and p70 S6 kinase. Conversely, we were able to show that this pathway was not involved in the signal transduction pathway mediating IL-10 inhibition of pro-inflammatory cytokine release from monocytes. We have extended these studies to investigate the induction of p75 tumour necrosis factor receptor (TNF-R) shedding, another anti-inflammatory property of IL-10. Using the inhibitors of PI 3-kinase (LY294002 and wortmannin) and an inhibitor of p70 S6 kinase activation (rapamycin), we were able to show that this anti-inflammatory effect of IL-10 was not mediated by the PI 3-kinase/p70 S6 kinase pathway, indicating that another signalling cascade(s) was involved. Further studies also investigated the role of tyrosine kinases in the response to IL-10. Two distinct tyrosine kinase inhibitors, herbimycin and genistein affected the expression of TNF-R in response to IL-10 but, surprisingly, with opposite effects. However, both compounds inhibited the activation of both PI 3-kinase and p70 S6 kinase, with a concomitant inhibition of IL-10-induced proliferation. We observed that whilst tyrosine kinase activity was involved in the regulation of TNF-R expression, IL-10-induced activation of JAK kinases was not sensitive to inhibition by the tyrosine kinase inhibitors. These data suggest that multiple unknown tyrosine kinases are mediating the IL-10-induced signal transduction pathways leading to the regulation of TNF-R expression and IL-10-induced proliferation.

Apoptosis modulation in mononuclear cells recovered from individuals exposed to Plasmodium falciparum infection

In endemic areas, asymptomatic infection by the malaria parasite Plasmodium falciparum was found associated with elevated percentages of human host's mononuclear cell spontaneous in-vitro apoptosis. In Dielmo, a village where malaria is holoendemic, apoptosis was age-and parasite-dependent. In-vitro exposure of peripheral blood mononuclear cells (PBMC) to the parasite extract induced a marked increase in the mononuclear cell membrane expression of functional CD95 antigen: a 3-h exposure of the mononuclear cells to anti-CD95 antibodies led to a detectable increase in the mean percentage of apoptotic nuclei found in the cultures carried out in the presence of P. falciparum extracts compared to control cultures. IL-2, IL-4, IL-6 and IL-10 promoted the viability of PBMC in cultures while IL-1alpha or IFN-gamma had no obvious impact and TNFalpha gave conflicting results. IL-2 was the most efficient cytokine at rescuing PBMC from cell death and this effect was associated with a strong increase in T cell activation. In contrast, IL-4 and IL-10 had no such effect on T cell activation, hence they acted as survival factors and not through their mitogenic activity. Taken together, these different observations suggested that the levels of in-vitro apoptosis observed were not only associated with parasite infection, but also potentially modulated by the human host through different pathways.

Recent advances in the molecular pathogenesis of lymphomas

Most human lymphomas remain heterogeneous biologic entities in spite of recent advances in the description of their clinical presentation, cellular morphology, immunophenotype, and genotype. Elucidation of genetic alterations causing malignant transformation may explain pathogenesis, refine differential diagnosis, clarify prognosis, and provide rational basis for new therapy. During the last year the expression of anaplastic lymphoma kinase clarified presentation and provided clues toward the outcome of anaplastic large cell lymphoma; the breakpoints of t(2;5) were mapped; constitutive activation of anaplastic lymphoma kinase by a chromosomal inversion was described; transformation was shown to be independent of nuclear localization of anaplastic lymphoma kinase; and phospholipase C-gamma was identified as a molecular target for the kinase activity of anaplastic lymphoma kinase. Molecular characterization of recurrent chromosome abnormalities has identified new candidate oncogenes: bcl-9, bcl-10, PAX-5, MMSET, and c-maf. Their precise role in malignant transformation, and the frequency of their alteration in lymphoma and myeloma, is not yet defined. The expression of the antiapoptotic protein bcl-2 on aggressive lymphomas was shown to be associated with inferior disease-free survival by several investigators. This may be a target of pharmacologic reduction of bcl-2 levels. Can these advances in molecular pathogenesis improve cure rates for lymphoma? The spectacularly successful molecular modeling of inhibitors for HIV protease suggests that this may be an attainable objective.

The regulation of apoptosis by microbial pathogens

In the past few years, there has been remarkable progress unraveling the mechanism and significance of eukaryotic programmed cell death (PCD), or apoptosis. Not surprisingly, it has been discovered that numerous, unrelated microbial pathogens engage or circumvent the host's apoptotic program. In this chapter, we briefly summarize apoptosis, emphasizing those studies which assist the reader in understanding the subsequent discussion on PCD and pathogens. We then examine the relationship between virulent bacteria and apoptosis. This section is organized to reflect both common and diverse mechanisms employed by bacteria to induce PCD. A short discussion of parasites and fungi is followed by a detailed description of the interaction of viral pathogens with the apoptotic machinery. Throughout the review, apoptosis is considered within the broader contexts of pathogenesis, virulence, and host defense. Our goals are to update the reader on this rapidly expanding field and identify topics in the current literature which demand further investigation.

Interleukin-10 levels are often elevated in serum of adults with Hodgkin's disease and are associated with inferior failure-free survival

BACKGROUND

Interleukin-10 (IL-10) is a pleiotropic cytokine that protects B- or T-lymphocytes and hemopoietic progenitors from apoptosis induced by doxorubicin, glucocorticoids, or deprivation of growth factors. IL-10 is also immunosupressive, and tumor cells secreting IL-10 can grow in syngeneic or allogeneic hosts, and can inhibit the generation of tumor-specific cytotoxic T cells. Hodgkin-Reed-Sternberg cells are derived from follicular center B cells and they may be latently infected by EBV. When this occurs they often express IL-10. Based on these considerations we investigated the relationship between pretreatment serum IL-10 levels and failure-free survival (FFS) in Hodgkin's disease (HD).

PATIENTS AND METHODS

Untreated patients, older than 16 years, with biopsy-proven HD, were included if treated with ABVD or equivalent regimens, and if pretreatment serum was available. IL-10 levels were determined with a capture enzyme-linked immunoassay specific for cellular IL-10.

RESULTS

Among healthy adult volunteers serum IL-10 levels ranged from 4.8-9.8 pg/ml (mean 7.1, standard deviation 1.5 pg/ml). Therefore levels > or = 10 pg/ml were considered elevated. We identified 101 patients with available serum. Their median age was 32 years, and 60% had B-symptoms. Ann Arbor stage was I in 4, II in 21, III in 35, and IV in 41 patients. Histology was nodular sclerosis in 74, mixed cellularity in 12, lymphocyte predominance in six, lymphocyte depletion in one, and unclassified in eight patients. Pretreatment serum IL-10 levels were elevated in 51 patients, and were higher in those with serum albumin < 3.5 g/dl, B symptoms, serum beta 2-microglobulin > or = 2.5 mg/l, anemia, and AAS III or IV. After a median follow-up of 32 months for survivors, 20 patients have progressed, and the three-year FFS of those with high vs. normal serum IL-10 was 60% +/- 9 vs. 91 +/- 9% (50% vs. 50% of the population; P = 0.004 by log-rank). Among patients with Ann Arbor stage III or IV the three-year FFS for those with high vs. normal serum IL-10 (58 vs. 42% of the population) was 57 +/- 9% vs. 92 +/- 6% (P = 0.008 by log-rank). Multivariate analysis using Cox's proportional hazards model confirmed that IL-10 was an independent variable associated with inferior FFS in this population.

CONCLUSIONS

Elevation of serum IL-10 levels is frequent and is associated with inferior FFS in adults with ABVD-treated HD. This observation should be verified in other patient populations. In addition, the source and the role of IL-10 in the biology of HD should be further investigated.

Interleukin-10 Abrogates the Inhibition of Epstein-Barr Virus–Induced B-Cell Transformation by Memory T-Cell Responses

In vitro infection of human B lymphocytes by Epstein-Barr virus (EBV) results in their growth transformation and establishment of immortalized lymphoblastoid cell lines. The virus was found to encode a homologue of the pleiotropic cytokine interleukin-10 (IL-10), which has wide-ranging effects on the immune system. We investigated the effect of human IL-10 (hIL-10) and viral IL-10 (vIL-10) on EBV-specific immunological memory, as assessed by the inhibition of EBV-induced B-cell transformation by the autologous T cells. We found that IL-10 abrogates the inhibitory capacity of T cells. This IL-10 effect is mediated through suppression of T-cell activation-induced IL-2 and interferon-γ production and through a direct enhancement of EBV-infected B-cell growth.

Interleukin-10 Abrogates the Inhibition of Epstein-Barr Virus–Induced B-Cell Transformation by Memory T-Cell Responses

In vitro infection of human B lymphocytes by Epstein-Barr virus (EBV) results in their growth transformation and establishment of immortalized lymphoblastoid cell lines. The virus was found to encode a homologue of the pleiotropic cytokine interleukin-10 (IL-10), which has wide-ranging effects on the immune system. We investigated the effect of human IL-10 (hIL-10) and viral IL-10 (vIL-10) on EBV-specific immunological memory, as assessed by the inhibition of EBV-induced B-cell transformation by the autologous T cells. We found that IL-10 abrogates the inhibitory capacity of T cells. This IL-10 effect is mediated through suppression of T-cell activation-induced IL-2 and interferon-γ production and through a direct enhancement of EBV-infected B-cell growth.

Nucleic acid sequence-based amplification, a new method for analysis of spliced and unspliced Epstein-Barr virus latent transcripts, and its comparison with reverse transcriptase PCR

Nucleic acid sequence-based amplification (NASBA) assays were developed for direct detection of Epstein-Barr virus (EBV) transcripts encoding EBV nuclear antigen 1 (EBNA1), latent membrane proteins (LMP) 1 and 2, and BamHIA rightward frame 1 (BARF1) and for the noncoding EBV early RNA 1 (EBER1). The sensitivities of all NASBAs were at least 100 copies of specific in vitro-generated RNA. Furthermore, 1 EBV-positive JY cell in a background of 50,000 EBV-negative Ramos cells (the relative sensitivity) was detected by using the EBNA1, LMP1, and LMP2 NASBA assays. The relative sensitivity of the EBER1 NASBA was 100 EBV-positive cells, which was probably related to the loss of small RNA molecules during the isolation. The BARF1 and LMP2 NASBAs were evaluated on clinical material. BARF1 expression was found in 6 of 7 nasopharyngeal carcinomas (NPC) but in 0 of 22 Hodgkin's disease (HD) cases, whereas LMP2 expression was found in 7 of 7 NPCs and in 17 of 22 HD cases. For detection of EBNA1 transcripts in HLs (n = 12) and T- and B-cell non-Hodgkin's lymphomas (n = 3 and n = 2, respectively), NASBA was compared with reverse transcriptase (RT) PCR. Two samples were positive only with NASBA, and two other samples were positive only with RT-PCR; for all other samples, the RT-PCR and NASBA results were in agreement. We conclude that NASBA is suitable for sensitive and specific detection of the above-mentioned EBV transcripts, regardless of their splicing patterns and the presence of EBV DNA. The EBNA1, LMP2, and BARF1 NASBAs developed in this study proved to be reliable assays for detection of the corresponding transcripts in EBV-positive clinical material.

Pathogenic Mycobacterium tuberculosis Evades Apoptosis of Host Macrophages by Release of TNF-R2, Resulting in Inactivation of TNF-α

Infection by Mycobacterium tuberculosis (MTB) induces human alveolar macrophage (AMφ) apoptosis by a TNF-α-dependent mechanism. The apoptotic response is postulated to be a defense mechanism, limiting the growth of this intracellular pathogen. Consistent with that model, recent studies showed that the virulent MTB strain H37Rv induces substantially less AMφ apoptosis than the attenuated strain H37Ra. We now report that AMφ infection with either H37Rv or H37Ra induces comparable levels of TNF-α measured by ELISA but that TNF-α bioactivity is reduced in supernatants of H37Rv-infected AMφ. Differential release of soluble TNFR2 (sTNFR2), with formation of inactive TNF-α-TNFR2 complexes accounted for the difference in TNF-α bioactivity in these cultures. Release of sTNFR2 by H37Rv-infected AMφ was IL-10 dependent since it was inhibited by neutralizing anti-IL-10 Ab. Thus, the effect of TNF-α produced by AMφ following infection can be modulated by virulent MTB, using IL-10 as an upstream mediator.

Serum cytokine levels in infectious mononucleosis at diagnosis and convalescence

Infection with the Epstein-Barr virus (EBV) is common worldwide. A significant number of infected individuals develop infectious mononucleosis (IM). IM is manifested in most patients as a benign disease with mild symptoms. However, serious complications may develop in a subset of patients. Because EBV-infected B lymphocytes produce various cytokines that may provide the cells with a proliferative advantage, cytokine concentrations in serum samples taken from IM patients were measured in order to identify the cytokines responsible for the clinical manifestations of the disease. The concentrations of interleukin-1beta (IL-1beta), IL-2, IL-6, IL-8, IL-10, tumor necrosis factor-alpha (TNF-alpha), and lymphotoxin (LT) were measured using an enzyme-linked immunosorbent assay (ELISA) in serum obtained from 14 IM patients during the acute phase of the disease and during convalescence, 5 patients with identical clinical manifestations who did not have IM (sick controls), and 11 healthy volunteers. It was found that the serum levels of TNF-alpha and IL-6 were significantly high in patients with acute IM compared with the serum levels in healthy individuals (P = 0.008 and P < 0.001, respectively) but returned to normal at convalescence (P = 0.009 and P = 0.005 respectively). However, whereas TNF-alpha concentrations were significantly higher (P = 0.04) in patients with acute IM than in the sick controls, no significant difference in IL-6 concentrations was found between the two groups of patients. Changes in IL-10 concentration were not statistically significant, and IL-1beta, IL-2, IL-8, and LT were detected only sporadically. The data in this study suggest that TNF-alpha may have a specific role in causing the clinical manifestations of IM. Further studies should determine the clinical significance of TNF-alpha inhibition in IM.

Synergistic effect between IL-10 and bcl-2 genotypes in determining susceptibility to systemic lupus erythematosus

OBJECTIVE

To determine whether genes participating in programmed cell death, including bcl-2, IL-10, Fas-L, and CTLA-4, may contribute to the genetic predisposition to systemic lupus erythematosus (SLE).

METHODS

First, intragenic markers for the bcl-2, IL-10, Fas-L, and CTLA-4 genes were characterized and their extent of polymorphism in normal populations was determined. The allelic distribution of these gene markers in a large Mexican American SLE cohort of 158 patients and 223 ethnically matched controls was determined using fluorescent-labeled primers and semiautomated genotyping.

RESULTS

The bcl-2, Fas-L, and IL-10 loci showed significantly different allelic distribution in SLE patients compared with controls, indicating an association between these genes and SLE. No association was found between SLE and the CTLA-4 gene. Further analysis revealed a synergistic effect between susceptibility alleles of the bcl-2 and IL-10 genes in determining disease susceptibility. Alone, the presence of each of these alleles was associated with a moderate increase in SLE risk, while the occurrence of these alleles together increased the odds of developing SLE by more than 40-fold.

CONCLUSION

The results suggest that individuals carrying specific genotypes of both bcl-2 and IL-10 are at significant risk of developing SLE.

Functional significance of cell volume regulatory mechanisms

To survive, cells have to avoid excessive alterations of cell volume that jeopardize structural integrity and constancy of intracellular milieu. The function of cellular proteins seems specifically sensitive to dilution and concentration, determining the extent of macromolecular crowding. Even at constant extracellular osmolarity, volume constancy of any mammalian cell is permanently challenged by transport of osmotically active substances across the cell membrane and formation or disappearance of cellular osmolarity by metabolism. Thus cell volume constancy requires the continued operation of cell volume regulatory mechanisms, including ion transport across the cell membrane as well as accumulation or disposal of organic osmolytes and metabolites. The various cell volume regulatory mechanisms are triggered by a multitude of intracellular signaling events including alterations of cell membrane potential and of intracellular ion composition, various second messenger cascades, phosphorylation of diverse target proteins, and altered gene expression. Hormones and mediators have been shown to exploit the volume regulatory machinery to exert their effects. Thus cell volume may be considered a second message in the transmission of hormonal signals. Accordingly, alterations of cell volume and volume regulatory mechanisms participate in a wide variety of cellular functions including epithelial transport, metabolism, excitation, hormone release, migration, cell proliferation, and cell death.

An increased prevalence of Epstein-Barr virus infection in young patients suggests a possible etiology for systemic lupus erythematosus

An unknown environmental agent has been suspected to induce systemic lupus erythematosus (lupus) in man. Prompted by our recent immunochemical findings, we sought evidence for an association between Epstein-Barr virus infection and lupus. Because the vast majority of adults have been infected with Epstein-Barr virus, we chose to study children and young adults. Virtually all (116 of 117, or 99%) of these young patients had seroconverted against Epstein-Barr virus, as compared with only 70% (107 of 153) of their controls (odds ratio 49.9, 95% confidence interval 9.3-1025, P < 0. 00000000001). The difference in the rate of Epstein-Barr virus seroconversion could not be explained by serum IgG level or by cross-reacting anti-Sm/nRNP autoantibodies. No similar difference was found in the seroconversion rates against four other herpes viruses. An assay for Epstein-Barr viral DNA in peripheral blood lymphocytes established Epstein-Barr virus infection in the peripheral blood of all 32 of the lupus patients tested, while only 23 of the 32 matched controls were infected (odds ratio > 10, 95% confidence interval 2.53-infinity, P < 0.002). When considered with other evidence supporting a relationship between Epstein-Barr virus and lupus, these data are consistent with, but do not in themselves establish, Epstein-Barr virus infection as an etiologic factor in lupus.

ICAM-1, soluble-CD23, and interleukin-10 concentrations in serum in renal-transplant recipients with Epstein-Barr virus reactivation

Primary and reactivated Epstein-Barr virus (EBV) infections after organ transplantation are associated with the development of posttransplant lymphoproliferative malignancies. Since viral reactivation frequently stays asymptomatic, early diagnosis and treatment are challenges during posttransplant patient monitoring. Both soluble-CD23 (sCD23) and intercellular adhesion molecule 1 (ICAM-1) cell surface expression as well as interleukin-10 (IL-10) production are closely associated with viral gene expression. Therefore, immunoglobulin M (IgM), IgG, IgA, sCD23, ICAM-1, and IL-10 concentrations were measured in serum samples from patients during EBV reactivation (n = 14) and were compared with those in samples from patients without EBV reactivation (n = 10) following renal transplantation. In addition, serum sCD23, ICAM-1, and IL-10 concentrations were measured longitudinally in weekly to biweekly samples from 10 patients with EBV reactivation for at least 20 weeks following transplantation. A significant elevation of sCD23 was found during viral reactivation (P < 0.05), whereas ICAM-1 levels showed a nonsignificant increase. The finding of a highly significant elevation of the serum IL-10 concentration during EBV reactivation (P < 0.001) may support speculations about its role in EBV-induced lymphoproliferation and in the development of opportunistic infections and secondary malignancies. Maximum serum IL-10 levels at the time of EBV reactivation were found in 7 of 10 patients. Well-defined ICAM-1 and sCD23 concentration peaks were found in 9 of 10 and 8 of 10 patients, respectively. Although both markers are not specific for EBV reactivation and therefore may not be useful for primary diagnosis, sCD23 and ICAM-1 might be potent tools for the clinical monitoring of EBV activity and virus-induced lymphoproliferation.

Interleukin-10 rescues T cells from apoptotic cell death: association with an upregulation of Bcl-2

We demonstrate that interleukin-10 (IL-10) can inhibit T-cell apoptosis. T cells, within a PBMC (peripheral blood mononuclear cell) population, were stimulated via the T-cell receptor and grown in the presence of IL-2. These cells had less apoptosis when in the continuous presence of IL-10, compared with cells grown in the absence of IL-10. Conversely, when stimulated and grown in the presence of neutralizing antibody of IL-10, there was an increase in T-cell apoptosis. The in vitro rescue from apoptotic cell death of other lymphoid cells, such as germinal centre B cells, has been shown by others to involve a Bcl-2 pathway. We therefore investigated whether IL-10 might affect the Bcl-2 expression on cultured T cells. By Western blotting we demonstrated that continuous exposure of IL-10 to T cells (within a PBMC population) enhanced the expression of Bcl-2. Furthermore, T cells protected from apoptotic cell death by IL-10 were indistinguishable from viable untreated cells in their ability to proliferate to either immobilized anti-CD3 or IL-2. Thus, we have shown that continuous culture of T cells in the presence of IL-10 will inhibit T-cell apoptosis because of, at least in part, the upregulation of Bcl-2, and this is associated with a normal proliferative function.

Inhibition of Fas-induced apoptotic cell death by osmotic cell shrinkage

Apoptosis is an active physiological mechanism permitting the elimination of cells by triggering an intracellular signalling cascade. Here, we tested whether osmotic alterations of cell volume interfere with apoptotic cell death in Jurkat T-lymphocytes. Apoptotic cell death of Jurkat cells was elicited by activation of the Fas receptor which results in sphingomyelinase stimulation, release of ceramide, activation of Ras, Rac-proteins and formation of O2. Osmotic cell shrinkage inhibited apoptotic cell death induced by the Fas receptor in Jurkat T-lymphocytes. Osmotic cell shrinkage did not interfere with Fas induced activation of the acidic sphingomyelinase or activation of Ras but impaired the formation of O2 suggesting an important function of cell volume in the synthesis of reactive oxygen intermediates upon Fas receptor ligation.

Apoptosis of myelin-reactive T cells induced by reactive oxygen and nitrogen intermediates in vitro

Apoptosis is a major mechanism of T cell elimination during ontogeny and tolerance induction as well as in autoimmunity. To assess the possible involvement of reactive oxygen and nitrogen intermediates (ROI and NO.) in T-cell apoptosis during autoimmune demyelination we investigated the effects of H2O2 and NO. in vitro on activated autoreactive CD4+ T cell lines capable of transferring experimental autoimmune encephalomyelitis (EAE) and experimental autoimmune neuritis (EAN). For detection and quantitation of apoptotic cells, DNA fragmentation was assessed by in situ tailing with fluorescein-ddUTP and subsequent flow cytometric analysis. H2O2 applied directly to the cell cultures for 6 to 18 hr at concentrations of 10 to 300 microM and ROI released by combination of hypoxanthine and xanthine oxidase (HX/XO) caused apoptosis in a dose-dependent manner in 13-33% of T cells of neuritogenic and encephalitogenic T cell lines. Apoptosis induction could be suppressed by the H2O2-neutralizing enzyme catalase. NO. released by the penicillamine derivative SNAP induced apoptosis to a similar extent as ROI. Maximum values were 38% in an encephalitogenic V beta 8.2-T cell receptor-bearing T cell line and 26% in a neuritogenic T cell line. T cell lines with specificity to ovalbumin revealed slightly lower susceptibility to apoptosis induction by all three kinds of trigger, which is, however, most probably not due to the different antigen specificity, but rather a result of fewer in vitro restimulation cycles of these cells. In neuritogenic cells high-dose (100 units/ml) exogenous interleukin-2 (IL-2) prevents H2O2-induced apoptosis. In conclusion, macrophage-derived reactive oxygen and nitrogen intermediates have the potency to limit inflammatory demyelination by elimination of autoreactive and bystander T cells via apoptotic cell death, and IL-2 is a rescue factor.

Unequal death in T helper cell (Th)1 and Th2 effectors: Th1, but not Th2, effectors undergo rapid Fas/FasL-mediated apoptosis

T helper cell (Th) 1, but not Th2, effectors undergo rapid Fas/Fas ligand (FasL)-mediated, activation-induced cell death upon restimulation with antigen. Unequal apoptosis is also observed without restimulation, after a longer lag period. Both effectors undergo delayed apoptosis induced by a non-Fas-mediated pathway. When Th1 and Th2 effectors are co-cultured, Th2 effectors survive preferentially, suggesting the responsible factor(s) is intrinsic to each population. Both Th1 and Th2 effectors express Fas and FasL, but only Th2 effectors express high levels of FAP-1, a Fas-associated phosphatase that may act to inhibit Fas signaling. The rapid death of Th1 effectors leading to selective Th2 survival provides a novel mechanism for differential regulation of the two subsets.

Fas and Fas ligand expression in the salivary glands of patients with primary Sjögren's syndrome

OBJECTIVE

To assess the role of Fas-mediated apoptosis in the salivary glands of patients with primary Sjögren's syndrome (SS).

METHODS

Expression of Fas, Fas ligand (FasL), and bcl-2 in salivary gland biopsy material was detected in situ by immunohistochemical staining and reverse transcriptase-polymerase chain reaction. DNA fragmentation in apoptotic cells was assessed by the enzymatic incorporation of labeled nucleotides (digoxigenin-dUTP).

RESULTS

The acinar epithelial cells in SS were Fas+ and FasL+, and these cells died by apoptosis. The majority of infiltrating lymphocytes in SS were Fas+ and bcl-2+, while few lymphocytes expressed FasL. In situ detection of apoptosis showed minimal cell death of lymphocytes, particularly in dense periductal foci. Lymphocytic cell death was significantly lower (P < 0.0001) in these foci compared with that in the interstitium.

CONCLUSION

Infiltrating lymphocytes in the focal lesions of the salivary glands of patients with SS are blocked in their ability to commit to apoptosis, even though they may express Fas. The presence of bcl-2 in these cells may explain their inability to undergo apoptosis. The acinar epithelial cells, in contrast, may undergo Fas-mediated apoptosis. These results suggest that the Fas death pathway may be an important mechanism leading to the glandular destruction found in SS.

The role of interleukin-10 in the inhibition of T-cell proliferation and apoptosis mediated by parainfluenza virus type 3

We have previously demonstrated that parainfluenza virus type 3 (PIV3), a significant respiratory pathogen, can markedly inhibit T-cell function in vitro. We now report that the virus potently induces interleukin-10 (IL-10) production by peripheral blood mononuclear cells. The IL-10 produced contributes to viral inhibition of T-cell proliferation and protects T cells from PIV3-mediated apoptosis. These findings suggest that IL-10 is likely to play an important immunoregulatory role in PIV3 infections.