Element Specificity of Transient Extreme Ultraviolet Magnetic Dichroism

In this work we combine theory and experiment to study transient magnetic circular dichroism (TRMCD) in the extreme ultraviolet spectral range in bulk Co and CoPt. We use the ab initio method of real-time time-dependent density functional theory to simulate the magnetization dynamics in the presence of short laser pulses. From this we demonstrate how TRMCD may be calculated using an approximation to the excited-state linear response. We apply this approximation to Co and CoPt and show computationally that element-specific dynamics of the local spin moments can be extracted from the TRMCD in the extreme ultraviolet energy range, as is commonly assumed. We then compare our theoretical prediction for the TRMCD for CoPt with experimental measurement and find excellent agreement at many different frequencies including the M_{23} edge of Co and N_{67} and O_{23} edges of Pt.

Magneto-Optical Functions at the 3p Resonances of Fe, Co, and Ni: Ab initio Description and Experiment

We present experimental data and a complete theoretical description of the magneto-optical contributions to the complex refractive index in the extreme ultraviolet (XUV) range covering the 3p resonances of Fe, Co, and Ni. The direct comparison of the two allows us to conclude that many-body corrections to the ground state and local field effects are crucial for an accurate description of M-edge spectra. Our results are relevant for investigation of static magnetization, via XUV spectroscopy of multielement systems, as well as the dynamics of magnetization, as needed in the study of femtomagnetism and spintronics.

[Brant goose colonies near snowy owls: internest distances in relation to lemming and arctic fox abundance]

Brant goose colonies around snowy owl nests have been studied near Meduza Bay (73 degrees 21' N, 80 degrees 32' E) and in the lower reaches of the Uboinaya River (73 degrees 37' N, 82 degrees 10' E), the northwestern Taimyr Peninsula, from 1999 to 2006. All brant nests within 680 m from an owl nest have been regarded as an individual colony. The results show that the area of the colony is always larger than the guarded area around the owl nest. In years of high abundance of lemmings, brant geese nest generally closer to the owl nest than in years of high abundance. When arctic foxes are abundant, however, brant geese nest significantly closer to owls than when the foxes are scarce, irrespective of lemming abundance. The mechanism of brant colony formation around owl nests is based on a number of stimuli.

OM197-MP-AC induces the maturation of human dendritic cells and promotes a primary T cell response

Dendritic cell (DC) maturation is critical for the induction of antigen-specific T lymphocyte responses and may be essential for the development of human vaccines relying on T cell immunity. We investigated the effects on human DC of OM-197, a synthetic pseudodipeptide derived from amino acids, linked to three fatty acid chains and devoid of endotoxin properties. OM-197 upregulated the expression of HLA-DR, CD80, CD86, CD83, CD40 and CD54 at the surface of myeloid DC naturally present in blood as well as of DC generated in vitro from monocytes using IL-4 and GM-CSF. OM-197 also induced the release of IL-12 and TNF-alpha from DC. Finally, DC incubated with OM-197 after pulsing with hepatitis B surface antigen (HBs Ag) induced in vitro expansion of IFN-gamma-secreting HBs Ag-specific CD4(+) T lymphocytes from naive individuals. Taken together, these data identify OM-197 as a potential vaccine adjuvant for the induction of Th1-type responses.

Medical abortion as an alternative to vacuum aspiration: first experiences with the 'abortion pill' in The Netherlands

OBJECTIVE

To establish to what extent medical abortion is desired as a supplement to existing care provision in The Netherlands and to establish the (dis)advantages of medical abortion versus surgical vacuum aspiration.

METHODS

The research project began in November 1999 and ended in September 2000. In two abortion clinics, the clients were asked to answer some questions about their expectations (before treatment) and their experiences with the treatment (at the post-treatment check-up). At the post-treatment check-up, the clients were also asked to fill out the Hopkin's Symptom Checklist (HSCL) which is an objective measure for the psychological and physical well-being of the clients during the previous week.

RESULTS

One hundred and thirty-one clients who chose medical abortion and 131 clients who chose surgical vacuum aspiration participated in the study. The failure rate was 3.3% for medical abortion and 1.5% for surgical vacuum aspiration. Of the medical abortion clients, 80.2% reported they were satisfied with this treatment and 68.1% said they would choose the same treatment procedure in the future. For vacuum aspiration, these figures were 92.9% and 83.2%, respectively. The most reported advantage of medical abortion was the fact that it was a pill, and no surgical procedures were necessary. The most reported disadvantages of medical abortion were the amount of blood loss and insecurity concerning the time of abortion.

CONCLUSIONS

Medical abortion seems to be a good supplement to the existing care provision in The Netherlands and should be offered in other clinics.

[Anti-tumor immunotherapy based on dendritic cells]

In cancer immunotherapy, the use of dendritic cells (DC) loaded with tumor-associated antigens (TAA) emerged as a promising strategy. We initiated 3 pilot clinical trials with immunological endpoints using TAA loaded autologous DC. These trials showed that this approach was safe and associated with the induction of potent TAA specific IFN-gamma responses, which were transient despite the providing a further help through KLH presentation. Subcutaneous (s.c.) IL-2 administration was associated with long-lasting TAA specific IL-5 production. Clinical responses were observed in about 1/3 of the patients. Further improvements will take advantage of the use of a new type of DC cells (IL-3/IFN-beta DC) and of tumor cell-DC hybrids.

Tumoricidal activity of monocyte-derived dendritic cells: evidence for a caspase-8-dependent, Fas-associated death domain-independent mechanism

Monocyte-derived dendritic cells (DC) were found to be cytotoxic for several tumor cell lines including Jurkat cells, which were killed through a calcium-independent pathway. K562 cells were resistant, excluding a NK cell-like activity. DC-mediated apoptosis did not involve classical death receptors because it was not reversed by blocking TNF/TNFR, CD95/CD95 ligand, or TNF-related apoptosis-inducing ligand/TNF-related apoptosis-inducing ligand receptor interactions. Fas-associated death domain-deficient, but not caspase-8 deficient, Jurkat cells were killed by DC. Indeed, caspase-8 cleavage was demonstrated in Jurkat cells cocultured with DC, and the use of specific caspase inhibitors confirmed that apoptosis triggered by DC was caspase-8 dependent. Furthermore, the involvement of Bcl-2 family members in the control of DC-mediated apoptosis was demonstrated by Bid cleavage in Jurkat cells cocultured with DC and resistance of Jurkat cells overexpressing Bcl-2 to DC-mediated cytotoxicity. Overall, these data indicate that monocyte-derived DC exert a caspase-8-dependent, Fas associated death domain-independent tumoricidal activity, a finding that could be relevant to their therapeutic use in cancer.

Human monocyte-derived dendritic cells produce bioactive gelatinase B: inhibition by IFN-beta

We studied the secretion of gelatinase B by dendritic cells (DC) generated by culturing human peripheral blood monocytes in granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-4 (IL-4). First, we found the intracellular expression of gelatinase B on sections of fixed DC pellets. Zymography analysis of the supernatants of DC cultured for 72 h demonstrated the presence of gelatinase B. To determine if DC produce net enzymatic activity, bioactive gelatinase, a novel sensitive fluorescent-activated substrate conversion (FASC) assay was used to complement the zymography data. Culture media of unstimulated DC demonstrated reproducible net gelatinolytic activity. Tumor necrosis factor-alpha (TNF-alpha) IL-1beta but not lipopolysaccharide (LPS) stimulation caused a significant increase in gelatinase B production in zymography analysis. Both types of stimulation failed to increase net gelatinase activity in FASC assay. Interestingly, interferon-beta (IFN-beta) significantly diminished both the total zymolytic production and the net bioactive gelatinase produced by DC in a dose-dependent manner. We conclude that human monocyte-derived DC secrete bioactive gelatinase B and that IFN-beta inhibits this production.

Deficient IL-12(p35) gene expression by dendritic cells derived from neonatal monocytes

To gain insight into the defects responsible for impaired Th1 responses in human newborns, we analyzed the production of cytokines by dendritic cells (DC) derived from cord blood monocytes. We observed that neonatal DC generated from adherent cord blood mononuclear cells cultured for 6 days in the presence of IL-4 and GM-CSF show a phenotype similar to adult DC generated from adherent PBMC, although they express lower levels of HLA-DR, CD80, and CD40. Measurement of cytokine levels produced by neonatal DC upon stimulation by LPS, CD40 ligation, or poly(I:C) indicated a selective defect in the synthesis of IL-12. Determination of IL-12(p40) and IL-12(p35) mRNA levels by real-time RT-PCR revealed that IL-12(p35) gene expression is highly repressed in stimulated neonatal DC whereas their IL-12(p40) gene expression is not altered. The addition of rIFN-gamma to LPS-stimulated newborn DC restored their expression of IL-12(p35) and their synthesis of IL-12 (p70) up to adult levels. Moreover, we observed that neonatal DC are less efficient than adult DC to induce IFN-gamma production by allogenic adult CD4(+) T cells. This defect was corrected by the addition of rIL-12. We conclude that neonatal DC are characterized by a severe defect in IL-12(p35) gene expression which is responsible for an impaired ability to elicit IFN-gamma production by T cells.

Role and expression of CD40 on human retinal pigment epithelial cells

PURPOSE

To examine the CD40 costimulatory molecule expression on normal resting or activated adult human retinal pigment epithelium (hRPE) cells and to evaluate its role as an activation molecule considering the potential antigen presentation functions of hRPE cells.

METHODS

Expression of HLA-DR and costimulatory (CD40, B7.1, B7.2, CD54, and CD58) molecules on hRPE cells was analyzed by flow cytometry. CD40 triggering was performed using soluble CD40L or cocultures with CD40L transfected fibroblasts. Interleukin (IL)-6, -8, -10, and -12 secretions were measured by enzyme-linked immunosorbent assay. Antigen presentation function of hRPE cells was assessed by coculturing hRPE cells with allogeneic T cells. T-cell proliferation was measured by [(3)H]-thymidine incorporation, and T-cell apoptosis by measurement of caspase-3 activity.

RESULTS

Interferon (IFN)gamma-activated hRPE cells expressed CD40, but not B7.1 or B7.2. Although interferongamma enhanced IL-6 and IL-8 production, CD40 triggering of IFNgamma-activated hRPE cells did not induce IL-12 secretion. hRPE cells did not stimulate allogeneic resting T cells and downregulated phytohemagglutinin-activated allogeneic T cells via a cell-to-cell contact-dependent mechanism. Some induction of apoptosis was detected.

CONCLUSIONS

CD40 is expressed on IFNgamma-activated hRPE cells. Its ligation leads to an increased production of IL-6 and IL-8 but fails to induce B7.1 or B7. 2 expression, or to induce IL-12 secretion. Accordingly, hRPE cells do not activate allogenic T cells but inhibit T-cell proliferation, partly through induction of apoptosis. These results suggest that hRPE cells could be implicated more in a deviant antigen presentation. If the exact molecular mechanisms are unclear, it is likely that CD40-CD40L interaction could play a role in this process.

Expression of c-FLIP(L) and resistance to CD95-mediated apoptosis of monocyte-derived dendritic cells: inhibition by bisindolylmaleimide

To gain insight into the mechanisms controlling apoptosis of dendritic cells (DC), human monocyte-derived DC were analyzed for their expression of CD95 (Fas/Apo-1) and their response to CD95 ligation. Although DC expressed the CD95 molecule on their membrane, they did not undergo apoptosis on CD95 ligation unless sensitized by cycloheximide. In parallel, DC synthesized c-FLIP(L), an inhibitor of the CD95-mediated death-signaling cascade. We also demonstrated that bisindolylmaleimide down-regulates c-FLIP(L) expression in DC and, in parallel, allows CD95-mediated apoptosis in these cells. In contrast, Bcl-2, Bcl-x(L), and Bax levels were not affected by bisindolylmaleimide. We conclude that DC resist CD95- mediated apoptosis in association with c-FLIP(L) expression and that the immunosuppressive potential of bisindolylmaleimide previously observed at the T-cell level also involves facilitation of CD95-mediated DC apoptosis.

Helper T-cell responses elicited by Der p 1-pulsed dendritic cells and recombinant IL-12 in atopic and healthy subjects

BACKGROUND

Environmental allergens, such as Dermatophagoides pteronyssinus group 1 antigen (Der p 1), induce T(H2)-type responses in atopic patients, whereas healthy individuals have T(H1)-type responses to the same antigens. Because of their efficient synthesis of IL-12, dendritic cells (DCs) are potent inducers of T(H1)-type immune responses.

OBJECTIVE

We sought to determine whether DCs would skew allergen-specific T(H2)-type responses from atopic individuals.

METHODS

Purified CD4(+) T cells from healthy donors or atopic individuals were cultured in the absence or presence of recombinant (r)IL-12 with DCs derived from PBMCs and pulsed with Der p 1. Supernatants of DC-T cell cocultures were assayed by ELISA for IL-5 and IFN-gamma.

RESULTS

A T(H1)-type response developed in purified CD4(+) T cells from healthy donors in response to Der p 1-pulsed DCs, as indicated by high levels of IFN-gamma in culture supernatants. In contrast, CD4(+) T cells from atopic donors displayed a T(H2)-type profile characterized by high levels of IL-5 and low levels of IFN-gamma. The addition of rIL-12 (10 ng/mL) to DC-T cell cocultures resulted in the induction of IFN-gamma secretion by Der p 1-specific CD4(+) T cells from atopic patients, whereas their production of IL-5 was not inhibited. Using flow cytometry after intracytoplasmic staining, we found that IFN-gamma and IL-5 were secreted by distinct CD4(+) T-cell subpopulations.

CONCLUSION

The cytokine profile of Der p 1-specific T(H2)-like cells from atopic individuals is maintained when the allergen is presented by DCs, even in the presence of exogenous rIL-12.

Natriuretic peptide receptors of type A in human neuroblastomas

Functional natriuretic peptide receptors of type A (NPR-A) were detected in the human neuroblastoma NB-OK-1, SK-N-SH and SK-N-BE, but not the SH-SY5Y, cell lines. Also, NPR-A mRNA was detected in 19 of the 25 tumor neuroblastoma samples tested in this study. Five of the eight tumor neuroblastoma samples that were assayed for atrial natriuretic peptide (ANP) binding revealed the presence of ANP-binding sites. In the human neuroblastoma NB-OK-1 cell line, [(3)H] thymidine incorporation was increased in response to ANP, decreased in response to pituitary adenylate cyclase-activating polypeptide (PACAP-27), and the stimulatory effect of ANP was inhibited by PACAP-27. Tissue transglutaminase activity was decreased by ANP and PACAP-27, and their effects were additive. However, neither cell cycle phases, cell growth, or cell apoptosis were modified by ANP or PACAP-27 treatments.

Down-regulation of interleukin-2 and interferon-gamma and maintenance of interleukin-4 and interleukin-10 production after administration of an anti-CD3 monoclonal antibody in mice

BACKGROUND

Activating anti-CD3 monoclonal antibodies (mAbs), such as OKT3, are potent immunosuppressive agents that are widely used in clinical transplantation. We investigated whether the in vivo induction of T cell unresponsiveness contributes to the immunosuppressive properties of the anti-mouse-CD3 mAb 145-2C11.

METHODS

After a single in vivo administration of 145-2C11 residual T cells were restimulated in vivo and in vitro to assess cytokine production. Mice were also transplanted with allogeneic skin 9 days after 145-2C11 administration to investigate whether the immunosuppressive properties of the antibody persist after the reexpression of the T cell receptor.

RESULTS

Pretreatment with anti-CD3 mAbs caused a profound deficit in both interleukin- (IL) 2 and interferon- (IFN) y secretion upon restimulation in vivo, whereas IL-4 was only partially inhibited and IL-10 production was significantly increased. Purified T cells obtained from mice injected with anti-CD3 mAb also displayed deficient IL-2 and IFN-gamma production together with persisting IL-4 and IL-10 secretion. 145-2C11 had immunosuppressive properties that per sisted after the reexpression of the T cell receptor because mice transplanted with allogeneic skin 9 days after a single anti-CD3 mAb injection still had significantly prolonged graft survival (14.1+/-0.6 days vs. 10.7+/-0.4 days in controls, P<0.02). Blocking IL-4 and IL-10 by neutralizing mAbs further prolonged skin graft survival in mice injected with 145-2C11 (18.3+/-0.7 vs. 14.8+/-0.6 days, P<0.02).

CONCLUSION

The in vivo administration of the 145-2C11 anti-CD3 mAb results in the selective inhibition of Thl-type cytokine secretion upon restimulation, which correlates with a state of immunosuppression. The persistent production of Th2-type cytokines does not contribute to the anti-CD3 mAb-mediated prolonged survival of skin allografts in our experimental model.

Trypanosoma cruzi infects human dendritic cells and prevents their maturation: inhibition of cytokines, HLA-DR, and costimulatory molecules

Trypanosoma cruzi, a parasitic protozoan, is the etiological agent of Chagas' disease. Despite the many immune system disorders recognized in this infection and the crucial role played by dendritic cells (DC) in acquired immune responses, it was not known whether these cells could be infected by T. cruzi trypomastigotes and the consequences of such an infection on their immune functions. We now provide evidence that human monocyte-derived DC can be infected by T. cruzi and can support its intracellular multiplication. Interestingly, this infection has functional consequences on immature DC and on their maturation induced by lipopolysaccharide (LPS). First, after T. cruzi infection, the basal synthesis of interleukin-12 (IL-12) and tumor necrosis factor alpha (TNF-alpha) was impaired. Furthermore, the process of maturation of DC induced by LPS was drastically affected by T. cruzi infection. Indeed, secretion of cytokines such as IL-12, TNF-alpha, and IL-6, which are released normally at high levels by LPS-activated DC, as well as the up-regulation of HLA-DR and CD40 molecules, was significantly reduced after this infection. The same effects could be induced by T. cruzi-conditioned medium, indicating that at least these inhibitory effects were mediated by soluble factors released by T. cruzi. Taken together, these results provide new insights into a novel efficient mechanism, directly involving the alteration of DC function, which might be used by T. cruzi to escape the host immune responses in Chagas' disease and thus might favor persistent infection.

Inhibition of human dendritic cell functions by methylprednisolone

BACKGROUND

The aim of this study was to better define how glucocorticoids influence primary human T cell responses. Dendritic cells (DC*) are the most effective antigen presenting cells able to activate naive T cells. Previous studies have shown that dexamethasone impaired the function of murine DC. Here, we analyzed how methylprednisolone (MP) might affect the function and maturation of human DC.

METHODS

Human DC were generated from peripheral blood mononuclear cells cultured in granulocyte macrophage-colony stimulating factor and interleukin (IL)4. DC maturation was induced either by lipopolysaccharide (LPS) or by fibroblast transfected with the CD40-ligand gene (3T6-CD40L). DC phenotype was characterized by flow cytometric analysis, their cytokine production by ELISA. The ability of DC to activate naive T cells was evaluated in mixed leukocyte reactivity.

RESULTS

Although MP did not affect viability of DC, it enhanced their antigen uptake and down-regulated their basal expression of CD86. The expression of CD80 and CD54 by DC was slightly decreased and HLA-DR expression was not modified. MP prevented LPS-induced DC maturation as assessed by the inhibition of CD86, CD80 and CD54 up-regulation, CD83 induction and production of TNF-alpha, IL-6, and IL-12. In contrast, when DC were stimulated by 3T6-CD40L, MP prevented only the synthesis of IL-12. Moreover, MP-treated DC were deficient in their ability to elicit proliferative responses of CD4+CD45RA+ allogeneic T cells as well as their synthesis of interferon (IFN)-gamma, IL-5, and IL-13. CONCLUSION. Glucocorticoids exert potent suppressive effects on human DC and thereby inhibit the induction of primary T cell responses.

IFN-beta interferes with the differentiation of dendritic cells from peripheral blood mononuclear cells: selective inhibition of CD40-dependent interleukin-12 secretion

We studied the effects of interferon-beta (IFN-beta) on the differentiation of dendritic cells (DC) obtained by culturing plastic-adherent peripheral blood mononuclear cells (PBMC) from a total of 30 healthy volunteers in the presence of granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-4 (IL-4). First, we found that the addition of IFN-beta at the initiation of the culture did not modify DC morphology but caused a reproducible and statistically significant upregulation of HLA-DR, CD86, and CD80 surface expression. CD1a expression was significantly reduced, and CD40 expression was unchanged. We then determined the influence of IFN-beta on the production of cytokines by DC. DC differentiated in the presence of IFN-beta secreted significantly less IL-12 (p40 and p70) both spontaneously and on activation by fibroblasts transfected with the CD40L gene. This effect of IFN-beta was dose dependent and selective, as it was not observed for IL-6, IL-8, and tumor necrosis factor-alpha (TNF-alpha). As a consequence, DC differentiated in the presence of IFN-beta induced significantly less IFN-gamma secretion by alloreactive T cells, whereas they were more efficient than control DC in eliciting IL-5 secretion. We conclude that the direct action of IFN-beta on DC causes inhibition of their ability to secrete IL-12 in response to CD40 ligation and to elicit Th1 type responses.

Interferon-beta inhibits Th1 responses at the dendritic cell level. Relevance to multiple sclerosis

Clinical studies have demonstrated beneficial effects of interferon-beta (IFN-beta) therapy in multiple sclerosis (MS) patients. However, the mechanism of action of IFN-beta in MS remains unknown. IFN-beta has even been demonstrated to enhance isolated T cell secretion of IFN-gamma, a cytokine proven to be deleterious in MS. However, IFN-beta inhibits IFN-gamma secretion of T cells, when they are stimulated by antigen presenting cells (APC). We therefore decided to study the effects of IFN-beta on the in vitro differentiation of dendritic cells (DC), a major class of APC. First, we found that the addition of IFN-beta at the initiation of the differentiation did not modify DC morphology, but enhanced the expression of molecules involved in antigen presentation (HLA-DR, B7/1 and B7/2). However, DC, differentiated in the presence of IFN-beta, secreted less interleukin-12 (IL-12) both spontaneously and upon activation by CD40-ligand bearing cells. As a consequence, DC differentiated in the presence of IFN-beta induced less IFN-gamma secretion by alloreactive T cells. We conclude that the direct action of IFN-beta on DC results in inhibition of their ability to secrete IL-12 and to elicit Thelper-1 (Th-1) type responses. These results are of particular interest in MS, in which a critical role for IL-12 has recently been suggested by a number of clinical and experimental observations.

N-acetyl-L-cysteine inhibits primary human T cell responses at the dendritic cell level: association with NF-kappaB inhibition

N-acetyl-L-cysteine (NAC) is an antioxidant molecule endowed with immunomodulatory properties. To investigate the effect of NAC on the induction phase of T cell responses, we analyzed its action on human dendritic cells (DC) derived from adherent PBMC cultured with IL-4 and granulocyte-macrophage CSF. We first found that NAC inhibited the constitutive as well as the LPS-induced activity of the transcription factor NF-kappaB. In parallel, NAC was shown to down-regulate the production of cytokines by DC as well as their surface expression of HLA-DR, CD86 (B7-2), and CD40 molecules both at the basal state and upon LPS activation. NAC also inhibited DC responses induced by CD40 engagement. The inhibitory effects of NAC were not due to nonspecific toxicity as neither the viability of DC nor their mannose receptor-mediated endocytosis were modified by NAC. Finally, we found that the addition of NAC to MLR between naive T cells and allogeneic DC resulted in a profound inhibition of alloreactive responses, which could be attributed to a defect of DC as APC-independent T cell responses were not inhibited by NAC. Altogether, our results suggest that NAC might impair the generation of primary immune responses in humans through its inhibitory action on DC.

Oxidative stress up-regulates IL-8 and TNF-alpha synthesis by human dendritic cells

In addition to their damaging effects, reactive oxygen intermediates exert a regulatory role on gene expression and cell apoptosis. In this study, we evaluated the effects of oxidative stress on human dendritic cells (DC), a cell type which is critical for the initiation of the immune response. For this purpose, we tested the effects of H2O2 on DC derived from adherent peripheral blood mononuclear cells cultured in the presence of granulocyte-macrophage colony-stimulating factor and IL-4. Despite a moderate increase of DC apoptosis in the presence of H2O2, we observed that H2O2 stimulated the production of IL-8 and TFN-alpha by DC in a dose-dependent manner. The induction of cytokine synthesis was found to depend on the oxidative properties of H2O2 as it was inhibited by the addition of catalase, and to require de novo protein synthesis as it was not observed in the presence of cycloheximide. These data suggest that DC could contribute to innate immunity through an enhanced production of inflammatory cytokines in response to oxidative stress.

Thermolabile methylenetetrahydrofolate reductase in coronary artery disease

BACKGROUND

Hyperhomocysteinemia, an independent and graded risk factor for coronary artery disease (CAD), may result from both environmental and hereditary factors. Methylenetetrahydrofolate reductase (MTHFR) catalyzes the conversion of methylenetetrahydrofolate to methyltetrahydrofolate, the methyl donor in the remethylation of homocysteine to methionine. A 677C-->T mutation in the MTHFR gene has been associated with elevated homocysteine concentrations in homozygous (+/+) individuals.

METHODS AND RESULTS

We assessed the frequency of this common mutation in 735 CAD patients from the Regression Growth Evaluation Statin Study (REGRESS), a lipid-lowering coronary-regression trial, and in 1250 population-based control subjects. Furthermore, the association between the mutation and serum homocysteine concentrations was studied. The frequency of the homozygous (+/+) mutation was 9.5% among patients versus 8.5% among control subjects, resulting in an odds ratio of 1.21 (95% confidence interval [CI], 0.87 to 1.68), relative to the (-/-) genotype. Homocysteine concentrations were significantly elevated in both (+/+) and (+/-) individuals compared with (-/-) individuals (median homocysteine levels, 15.4, 13.4, and 12.6 micromol/L, for (+/+), (+/-), and (-/-) individuals, respectively). For a summary estimation of the risk of the (+/+) genotype for CAD, we performed a meta-analysis on 8 different case-control studies on thermolabile MTHFR in CAD. In the meta-analysis, the homozygous (+/+) genotype was present in 299 of 2476 patients (12.1%) and in 257 (10.4%) of 2481 control subjects, resulting in a significant odds ratio of 1.22 (95% CI, 1.01 to 1.47) relative to the (-/-) genotype.

CONCLUSIONS

Both the homozygous (+/+) and heterozygous (+/-) genotype result in elevated homocysteine concentrations. From our meta-analysis, we conclude that the homozygous (+/+) genotype is a modest but significant risk factor for CAD.

Human dendritic cell responses to lipopolysaccharide and CD40 ligation are differentially regulated by interleukin-10

We evaluated the effects of interleukin (IL)-10 on the maturation of human dendritic cells (DC) induced either by lipopolysaccharide (LPS) or CD40 engagement. For this purpose, DC generated by culturing plastic-adherent peripheral blood mononuclear cells for 7 days with granulocyte/macrophage-colony-stimulating factor and IL-4 were incubated for 3 days with either LPS (10 ng/ml) or 3T6 fibroblasts transfected with the gene encoding CD40 ligand, in absence or presence of IL-10. First we found that the membrane expression of CD83, a marker of mature DC, was inhibited by IL-10 when induced by LPS but not by CD40 engagement. Likewise, IL-10 inhibited LPS-induced but not CD40-dependent CD86 (B7.2) up-regulation on DC. Furthermore, IL-10 inhibited the production of IL-8 and tumor necrosis factor-alpha by DC when activated by LPS but not by CD40. In contrast, IL-10 inhibited IL-12 production in both activation systems. We conclude that IL-10 differentially influences LPS-dependent and CD40-dependent pathways of DC maturation.

Cloning of human IL-12 p40 and p35 DNA into the Semliki Forest virus vector: expression of IL-12 in human tumor cells

IL-12 can enhance the development of effective immune responses against tumors as well as against certain infectious agents. It is therefore a potential candidate for therapeutic use in cancer therapy and in the design of vaccines against several infectious diseases. Several studies have demonstrated that IL-12 could efficiently induce tumor regression in animal models. To investigate the antitumor effect of direct gene transfer of human IL-12 into tumors, human IL-12 p35 and p40 cDNAs were cloned into the Semliki Forest virus (SFV) vector pSFV1. In order to express the two subunits from the same vector, the p35 and the p40 cDNAs were cloned into pSFV1, each under the control of a subgenomic SFV promoter. Recombinant RNA produced by in vitro transcription of SFV-IL-12 construct, was packaged into SFV viral particles with the use of a non-packageable helper RNA. We show that human tumor cell lines infected in vitro in vivo with recombinant SFV-IL-12 viral particles secrete high levels of biologically active heterodimeric p35/p40 IL-12, as demonstrated using ELISA and biological assays.

Bacterial lipopolysaccharide stimulates the production of cytokines and the expression of costimulatory molecules by human peripheral blood dendritic cells: evidence for a soluble CD14-dependent pathway

To investigate the responses of dendritic cells (DC) during Gram-negative infections, we analyzed the effects of graded doses of LPS on the cytokine profile, phenotype, and allostimulatory potential of human DC generated by culturing plastic-adherent PBMC in presence of IL-4 and granulocyte-macrophage-CSF. First, we found that LPS stimulates the production of high levels of TNF-alpha, IL-6, IL-8, IL-12 by DC and up-regulates their expression of HLA-DR, B7-1, B7-2, and CD40. The effects of LPS were dose dependent, with a significant stimulatory effect already observed at a concentration of 0.1 ng/ml and a plateau being reached at 10 ng/ml. These phenotypic changes correlated with increased allostimulatory properties of LPS-activated DC because DC treated with LPS were significantly more efficient than untreated DC in eliciting IL-2 and IFN-gamma synthesis by alloreactive T cells and stimulating their proliferation. Experiments using neutralizing anti-IL-12 mAb indicated that LPS-induced IL-12 is responsible for the increased production of IFN-gamma but not for the increased proliferation during MLR. Finally, we observed that the DC responses to low levels of LPS (1 ng/ml) were dramatically inhibited by a blocking anti-CD14 mAb, although DC do not express CD14 molecules on their membrane. Experiments using serum depleted of soluble CD14 (sCD14) and sCD14 either purified from human serum or in recombinant form further established that DC respond to LPS via a soluble CD14-dependent pathway.

Bacterial lipopolysaccharide stimulates the production of cytokines and the expression of costimulatory molecules by human peripheral blood dendritic cells: evidence for a soluble CD14-dependent pathway

To investigate the responses of dendritic cells (DC) during Gram-negative infections, we analyzed the effects of graded doses of LPS on the cytokine profile, phenotype, and allostimulatory potential of human DC generated by culturing plastic-adherent PBMC in presence of IL-4 and granulocyte-macrophage-CSF. First, we found that LPS stimulates the production of high levels of TNF-alpha, IL-6, IL-8, IL-12 by DC and up-regulates their expression of HLA-DR, B7-1, B7-2, and CD40. The effects of LPS were dose dependent, with a significant stimulatory effect already observed at a concentration of 0.1 ng/ml and a plateau being reached at 10 ng/ml. These phenotypic changes correlated with increased allostimulatory properties of LPS-activated DC because DC treated with LPS were significantly more efficient than untreated DC in eliciting IL-2 and IFN-gamma synthesis by alloreactive T cells and stimulating their proliferation. Experiments using neutralizing anti-IL-12 mAb indicated that LPS-induced IL-12 is responsible for the increased production of IFN-gamma but not for the increased proliferation during MLR. Finally, we observed that the DC responses to low levels of LPS (1 ng/ml) were dramatically inhibited by a blocking anti-CD14 mAb, although DC do not express CD14 molecules on their membrane. Experiments using serum depleted of soluble CD14 (sCD14) and sCD14 either purified from human serum or in recombinant form further established that DC respond to LPS via a soluble CD14-dependent pathway.

Interleukin-10 prevents the generation of dendritic cells from human peripheral blood mononuclear cells cultured with interleukin-4 and granulocyte/macrophage-colony-stimulating factor

We evaluated the effects of interleukin (IL)-10 on the differentiation of dendritic cells (DC) obtained by culturing plastic-adherent peripheral blood mononuclear cells for 7 days in presence of granulocyte/macrophage-colony-stimulating factor (GM-CSF) + IL-4. The addition of IL-10 at the initiation of culture resulted in the generation of macrophage-like cells with expressing high levels of CD14 and decreased levels of CD1a and CD1c. Furthermore, cells generated in presence of IL-10 secreted lower levels of IL-12, but higher levels of IL-8 compared with DC generated in absence of IL-10, both spontaneously and after CD40 engagement. Finally, cells generated in presence of IL-10 were less efficient than DC in stimulating the production of IL-2, interferon-gamma, and IL-4 by allogeneic T cells. We conclude that IL-10 prevents the generation of DC induced by GM-CSF + IL-4 and favors the development of macrophages with a lower T cell stimulatory potential, but secreting higher levels of IL-8 than DC.

CD40 engagement induces monocyte procoagulant activity through an interleukin-10 resistant pathway

Interactions between membrane-bound molecules were previously shown to be involved in the induction of tissue factor-dependent monocyte procoagulant activity (PCA) by activated T cells. To investigate the potential role of the CD40/CD40 ligand (CD40L) pathway in this process, we first determined the effects of blocking anti-CD40 or anti-CD40L monoclonal antibodies (mAb) on the development of monocyte PCA during mixed lymphocyte reaction (MLR) between allogeneic peripheral blood mononuclear cells (PBMC). The strong inhibitory effect exerted by both mAb (mean percentages of inhibition: 88 and 91% for anti-CD40 and anti-CD40L mAb, respectively) indicates that CD40/CD40L interactions are required for the induction of PCA in MLR. These data led us to measure monocyte PCA after incubation of PBMC or purified monocytes with a stimulating anti-CD40 mAb (BL-C4) or with 3T6 fibroblasts transfected with the gene encoding CD40L. In both systems, we found that CD40 engagement strongly induced monocyte PCA which was related to tissue factor expression as shown by flow cytometric analysis. Finally, we observed that recombinant interleukin (IL)-10, which inhibits lipopolysaccharide-induced PCA, did not significantly influence CD40-dependent PCA. We conclude that CD40 engagement on monocytes induces tissue factor-dependent PCA through an IL-10-resistant pathway. These findings have implications for the control of coagulation events triggered by interactions between T cells and monocytes.

The induction of human T cell unresponsiveness by soluble anti-CD3 mAb requires T cell activation

In order to obtain an in vitro model of human T cell unresponsiveness induced by soluble anti-CD3 mAb in the presence of accessory cells, T cells purified from peripheral blood of healthy volunteers were cultured for 4 days with irradiated accessory cells and OKT3. After a 48 h resting period allowing TCR-CD3 complex re-expression, T cells were rechallenged with plastic-immobilized OKT3, and their proliferative response as well as their secretion of IL-2, IFN-gamma and IL-10 measured. Primary culture with OKT3 induced a state of unresponsiveness characterized by defective responses to OKT3 rechallenge but normal or enhanced responses to PMA and A23187 calcium ionophore, indicating a defect in the early steps of TCR-CD3-mediated signal transduction. Indeed, we found that unresponsive T cells displayed an impaired mobilization of intracellular calcium stores upon TCR-CD3 ligation. In order to determine whether the development of unresponsiveness depends on the initial T cell activation triggered by OKT3, we compared several versions of OKT3 differing in their ability to bind Fc receptors. We found that only the activating antibodies that bind Fc receptors on accessory cells induced T cell unresponsiveness. We conclude that human resting T cells can be rendered unresponsive by anti-CD3 mAb in soluble form provided that they trigger T cell activation.

Interleukin-10 differentially regulates B7-1 (CD80) and B7-2 (CD86) expression on human peripheral blood dendritic cells

Most of the immunosuppressive effects of interleukin-10 (IL-10) are related to functional inhibition of antigen-presenting cells (APC). Herein, we investigate the influence of recombinant (r)IL-10 on human dendritic cells (DC) purified from peripheral blood of healthy volunteers. First, we found that rIL-10 inhibited in a dose-dependent manner the proliferative responses as well as the production of IL-2 and interferon-gamma (IFN-gamma) in mixed lymphocyte reaction (MLR) between purified T cells and DC. This rIL-10 effect could be attributed to a direct effect on DC, as DC preincubated with rIL-10 were found to be deficient in the induction of alloreactive T cells even when anti-IL-10 neutralizing mAb was added at the time of MLR. Flow cytometric analysis indicated that rIL-10 did not modify the expression of ICAM-1 (CD54) and B7-1 (CD80), but decreased HLA-DR and B7-2 (CD86) expression at the DC surface. We conclude that the inhibitory effect of rIL-10 on primary alloreactive T cell responses involves down-regulation of class II MHC and B7-2 expression at the DC surface.

B7/CD28-dependent IL-5 production by human resting T cells is inhibited by IL-10

We analyzed the effects of rIL-10 on IL-5 production by human resting T cells isolated from peripheral blood. Resting T cells of healthy individuals required activation for 48 h with either anti-CD3 mAb cross-linked on B7/CD32-transfected mouse fibroblasts or PMA in conjunction with anti-CD28 mAb for optimal IL-5 secretion. In each condition, IL-5 secretion measured by ELISA was inhibited in a dose-dependent manner by rIL-10, whereas IFN-gamma production was not suppressed. The inhibitory effect of rIL-10 on IL-5 synthesis induced by PMA and anti-CD28 mAb was also observed at the mRNA level. In contrast with its action on T cells costimulated by B7/CD28 signaling, rIL-10 did not block IL-5 secretion in response to PMA and A23187 calcium ionophore. The inhibition of IL-5 production by rIL-10 was not due to IL-2 deprivation because it was not modified by the addition of exogenous rIL-2. Moreover, cyclosporin A, which inhibited IL-2 more efficiently than rIL-10 in response to anti-CD3 mAb and B7/CD32 transfected fibroblasts, did not reduce and even enhanced IL-5 production. Finally, we analyzed the influence of endogenously produced IL-10 on IL-5 secretion by T cells stimulated by PMA and anti-CD28 mAb. Addition of a neutralizing anti-IL-10 mAb increased IL-5 release in this system, indicating that endogenous IL-10 controls IL-5 production. We conclude that both rIL-10 and endogenous IL-10 inhibit IL-5 production by T cells costimulated by B7/CD28 signaling.

B7/CD28-dependent IL-5 production by human resting T cells is inhibited by IL-10

We analyzed the effects of rIL-10 on IL-5 production by human resting T cells isolated from peripheral blood. Resting T cells of healthy individuals required activation for 48 h with either anti-CD3 mAb cross-linked on B7/CD32-transfected mouse fibroblasts or PMA in conjunction with anti-CD28 mAb for optimal IL-5 secretion. In each condition, IL-5 secretion measured by ELISA was inhibited in a dose-dependent manner by rIL-10, whereas IFN-gamma production was not suppressed. The inhibitory effect of rIL-10 on IL-5 synthesis induced by PMA and anti-CD28 mAb was also observed at the mRNA level. In contrast with its action on T cells costimulated by B7/CD28 signaling, rIL-10 did not block IL-5 secretion in response to PMA and A23187 calcium ionophore. The inhibition of IL-5 production by rIL-10 was not due to IL-2 deprivation because it was not modified by the addition of exogenous rIL-2. Moreover, cyclosporin A, which inhibited IL-2 more efficiently than rIL-10 in response to anti-CD3 mAb and B7/CD32 transfected fibroblasts, did not reduce and even enhanced IL-5 production. Finally, we analyzed the influence of endogenously produced IL-10 on IL-5 secretion by T cells stimulated by PMA and anti-CD28 mAb. Addition of a neutralizing anti-IL-10 mAb increased IL-5 release in this system, indicating that endogenous IL-10 controls IL-5 production. We conclude that both rIL-10 and endogenous IL-10 inhibit IL-5 production by T cells costimulated by B7/CD28 signaling.

Interleukin-10 inhibits B7 and intercellular adhesion molecule-1 expression on human monocytes

There is evidence that interleukin -10(IL-10) interferes with the costimulatory properties of antigen-presenting cells and, thereby, inhibits their ability to induce T cell activation. To determine whether this effect might involve modulation of the expression of accessory molecules, we analyzed by flow cytometry the influence of human IL-10 on the basal expression of intercellular adhesion molecule 1 (ICAM-1) as well as on the interferon gamma (IFN-gamma)-induced up-regulation of ICAM-1 and B7 at the surface of human monocytes. IL-10 inhibited both the basal expression and the IFN-gamma-induced ICAM-1 up-regulation. IL-10 also reduced B7 up-regulation on IFN-gamma-stimulated monocytes. The inhibitory effect of IL-10 both on ICAM-1 and B7 expression was shown to be dose dependent. We conclude that the ability of IL-10 to decrease both ICAM-1 and B7 expression on monocytes might contribute to its immunosuppressive properties.

A private idiotype can become recurrent through genetic recombination and gene(s) unlinked to the Igh locus governs its expression

Any immune response is characterized by its idiotypic profile. Two different kinds of idiotype (Id) have been described. Private Id are restricted to a few individuals from a species while recurrent Id appear in a large majority of individuals from the same species immunized with the same antigen. We describe, in this report, an experimental model whereby a private Id can become recurrent through genetic recombination. The immune response of A mice against the hapten arsonate is characterized by a recurrent Id called cross-reactive idiotype A (CRIA). A strongly CRI, called CRIA-like, can be occasionally detected in some BALB/c mice (5% to 10%) immunized with arsonate. Molecular studies show that CRIA and CRIA-like antibodies have highly homologous D segments and identical light chains. By contrast, their VH segments are vastly dissimilar. We have examined the anti-arsonate response of inbred strains of mice whose Igh loci are recombinant between those of A/He and BALB/c. Interestingly, we have observed that the CRIA-like Id which is private in BALB/c becomes recurrent in the AXC-1 strain which harbors the VH genes from BALB/c, the DH and CH genes from A/He. Structural studies demonstrate that highly homologous, VH, VL and D segments are used in BALB/c and AXC-1 mice. The basis for this differential expression of highly similar genes could be linked to the DH locus. However, F1 mice stemming from the cross between AXC-1 and BALB/c do not express the Id. The backcross analysis shows that the non-expression of the Id in F1 mice depends on genes unlinked to the Igh locus.