Antisense deoxyoligonucleotides or antibodies to murine MD-1 inhibit rejection of allogeneic and xenogeneic skin grafts in C3H mice

Inhibition of myeloid differentiation 1 specifically in colon with antisense oligonucleotide exacerbates dextran sodium sulfate-induced colitis

Myeloid differentiation 1 (MD-1), also known as lymphocyte antigen 86 (Ly86), is a soluble protein homologous to MD-2 and forms a complex with radioprotective 105 (RP105). RP105/MD-1 complex negatively regulates toll-like receptor 4 (TLR4) signaling and is involved in several immune disorders. However, the precise role of MD-1 in inflammatory bowel diseases (IBD) remains poorly understood. To further investigate the involvement of MD-1 in IBD, we inhibited MD-1 in colon with antisense oligonucleotide (AS-ODN) and assessed the effect of MD-1 inhibition on dextran sodium sulfate (DSS)-induced colitis. We discovered that MD-1 protein expression was remarkably decreased in both patients with ulcerative colitis and mice with DSS-induced colitis. For the first time, we showed that oral administration of MD-1 AS-ODN to mice significantly suppressed the MD-1 protein levels in colon rather than systemic tissues. Subsequently, we found that MD-1 AS-ODN treated mice were more susceptible to DSS-induced colitis based on loss of body weight, colon length, histological scores, and disease activity index. MD-1 inhibition also significantly enhanced inflammatory cytokines production such as IL-6 and IL-1β in colons. Finally, mice treated with MD-1 AS-ODN exhibited increased messenger RNA levels of TLR4 and MyD88 after DSS exposure and showed enhanced nuclear factor (NF)-κB activation compared with the control. Taken together, specifically suppression of MD-1 in colon tissues with AS-ODN exacerbates DSS-induced experimental colitis in mice, which is possibly related to activation of TLR4/NF-κB signaling.

Development of antibody-tagged nanoparticles for detection of transplant rejection using biomagnetic sensors

Organ transplantation is a life-saving procedure and the preferred method of treatment for a growing number of disease states. The advent of new immunosuppressants and improved care has led to great advances in both patient and graft survival. However, acute T-cell-mediated graft rejection occurs in a significant quantity of recipients and remains a life-threatening condition. Acute rejection is associated with decrease in long-term graft survival, demonstrating a need to carefully monitor transplant patients. Current diagnostic criteria for transplant rejection rely on invasive tissue biopsies or relatively nonspecific clinical features. A noninvasive way is needed to detect, localize, and monitor transplant rejection. Capitalizing on advances in targeted contrast agents and magnetic-based detection technology, we developed anti-CD3 antibody-tagged nanoparticles. T cells were found to bind preferentially to antibody-tagged nanoparticles, as identified through light microscopy, transmission electron microscopy, and confocal microscopy. Using mouse skin graft models, we were also able to demonstrate in vivo vascular delivery of T-cell targeted nanoparticles. We conclude that targeting lymphocytes with magnetic nanoparticles is conducive to developing a novel, noninvasive strategy for identifying transplant rejection.

Hyperbaric oxygen therapy as a sole agent is not immunosuppressant in a highly immunogenic mouse model

Background. Hyperbaric oxygen (HBO) therapy, which is used for many conditions, may also have immunosuppressive effects and could be used for prevention or treatment of graft-versus-host disease (GvHD). If HBO is immunosuppressant, then we hypothesize that HBO therapy will delay the T-cell mediated skin graft rejection. Methods. C57/BL6 black-coated (H2B) mice received skin graft from CBA (H2D) white-coated mice. Mice were treated with either 19 session of 240 kpa oxygen or 29 session of 300 kpa oxygen, for 90 minutes. Mice were housed either 4 per cage or separately, to prevent friction and mechanical factors that may affect graft survival. Skin grafts were assessed daily. Results. There was no difference in length of graft survival between mice that received either regimens of HBO therapy and mice that did not receive HBO therapy. Conclusions. HBO therapy, as a sole agent, did not delay skin graft rejection in a highly immunogenic mouse model.

Crystal structure of soluble MD-1 and its interaction with lipid IVa

Lipopolysaccharide (LPS) of Gram-negative bacteria is a common pathogen-associated molecular pattern (PAMP) that induces potent innate immune responses. The host immune response against LPS is triggered by myeloid differentiation factor 2 (MD-2) in association with Toll-like receptor 4 (TLR4) on the cell surface. The MD-2/TLR4-mediated LPS response is regulated by the evolutionarily related complex of MD-1 and Toll-like receptor homolog RP105. Here, we report crystallographic and biophysical data that demonstrate a previously unidentified direct interaction of MD-1 with LPS. The crystal structure of chicken MD-1 (cMD-1) at 2.0 A resolution exhibits a beta-cup-like fold, similar to MD-2, that encloses a hydrophobic cavity between the two beta-sheets. A lipid-like moiety was observed inside the cavity, suggesting the possibility of a direct MD-1/LPS interaction. LPS was subsequently identified as an MD-1 ligand by native gel electrophoresis and gel filtration analyses. The crystal structure of cMD-1 with lipid IVa, an LPS precursor, at 2.4 A resolution revealed that the lipid inserts into the deep hydrophobic cavity of the beta-cup-like structure, but with some important differences compared with MD-2. These findings suggest that soluble MD-1 alone, in addition to its complex with RP105, can regulate host LPS sensitivity.

Induction of tolerogenic vs immunogenic dendritic cells (DCs) in the presence of GM-CSF is regulated by the strength of signaling from monophosphoryl lipid A (MPLA) in association with glutathione and fetal hemoglobin gamma-chain

Previous studies showed a fetal sheep liver extract (FSLE), in association with monophosphoryl lipid A, MPLA (a bioactive component of lipid A of LPS), could interact to induce the development of dendritic cells (DCs) which regulated production of Foxp3+ Treg. This interaction was associated with an altered gene expression both of distinct subsets of TLRs and of CD200Rs. Prior studies had suggested that major interacting components within FSLE were gamma-chain of fetal hemoglobin (Hgbgamma) and glutathione (GSH). We investigated whether differentiation/maturation of DCs in vitro in the presence of either GM-CSF or Flt3L to produce preferentially either immunogenic or tolerogenic DCs was itself controlled by an interaction between MPLA, GSH and Hgbgamma. At low (approximately 10 microg/ml) Hgbgamma concentrations, DCs developing in culture with GSH and MPLA produced optimal stimulation of allogeneic CTL cell responses in vitro (and enhanced skin graft rejection in vivo). At higher concentrations (>40 microg/ml Hgbgamma) and equivalent concentrations of MPLA and GSH, the DCs induce populations of Treg which can suppress the induction of allogeneic CTL and graft rejection in vivo. These different populations of DCs express different patterns of mRNAs for the CD200R family. Addition of anti-TLR or anti-MD-1 mAbs to DCs developing in this mixture (Hgbgamma+GSH+MPLA), suggests that one effect of (GSH+Hgbgamma) on MPLA stimulation may involve altered signaling through TLR4.

15-deoxyspergualin prevents mucosal injury by inhibiting production of TNF-α and down-regulating expression of MD-1 in a murine model of TNBS-induced colitis

The immunosuppressive drug 15-deoxyspergualin (DSG) is currently being used in clinical trials to prolong graft survival and reverse graft rejection. Here we evaluated whether DSG has a potential for ameliorating diseases characterized by mucosal inflammation. Using a murine model of 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis, we were able to demonstrate that DSG reduced the severity of colitis. Therefore, colitic mice pretreated with DSG showed a striking improvement of the wasting disease compared with colitic mice, as assessed by weight loss as well as clinical, macroscopic and microscopic analysis. Also, we observed the significant change occurred in the CD19(+) B cell subset, which was decreased 15% in DSG pretreated colitic mice compared with colitic mice. However, DSG pretreatment does not influence the apoptotic population of T and B cells. Compared with colitic mice, down-regulation of TNF-alpha production was observed in DSG pretreated colitic mice. In addition, DSG pretreated colitic mice significantly reduced expression of MD-1 compared with colitic mice on B cells and dendritic cells (DCs). Therefore, pretreatment with DSG resulted in a significant histologic improvement, protecting against mucosal ulcerations and reduced inflammatory response by modulating expression of MD-1, which plays a very important role in immune response on B cells and DCs. Also, this improvement was paralleled by a reduction in TNF-alpha levels. Collectively, current results demonstrate that DSG may be an effective agent for the treatment of diseases characterized by mucosal inflammation.

MD1 expression regulates development of regulatory T cells

Intense interest has centered around the role of a subset of regulatory T cells, CD4+CD25+ Treg, in controlling the development of autoimmune disorders, allograft rejection, infection, malignancy, and allergy. We previously reported that MD1, a molecule known to be important in regulation of expression of RP105, also was important in regulating alloimmunity, and that blockade of expression of MD1 diminished graft rejection in vivo. One mechanism by which an MD1-RP105 complex exerts an effect on immune responses is through interference with an LPS-derived signal delivered through the CD14-MD-2-TLR4 complex. We show below that LPS signaling for Treg induction occurs at higher LPS thresholds that for effector T cell responses. In addition, blockade of MD1 functional activity in dendritic cells (using anti-MD1 mAbs, MD1 antisense deoxyoligonucleotides, or responder cells from mice with deletion of the MD1 gene), resulted in elevated Treg induction in response to allogeneic stimulation (in vivo or in vitro) in the presence of LPS. These data offer one mechanistic explanation for the augmented immunosuppression described following anti-MD1 treatment.

Inhibition of MD-1 expression by immunosuppressants or antisense oligodeoxynucleotides on skin allograft survival in mice

AIM

The aim of this study was to investigate the effects of inhibition of MD-1 expression using nonspecific immunosuppressants and specific antisense oligodeoxynucleotides (AS-ODNs) treatment on skin allograft survival in mice.

METHODS

C57BL/6 to Balb/c skin allograft model was used in all groups, followed by Cyclosporine (CsA), Tacrolimus (FK506), Mycophenolate Mofetil (MMF), and Sirolimus (SRL) intraperitaneally, as well as AS-ODNs intravenously. Recipients were humanely killed at 11 days after transplantation. MD-1 expression was determined using flow cytometric analysis (FACS). AlamarBlue was used to evaluate proliferation. And serum levels of interleukin (IL)-2 and IL-10 were detected using enzyme-linked immunosorbent assay (ELISA).

RESULTS

Compared with saline controls, the mean survival times (MST) of skin allografts in all of the immunosuppressants and AS-ODNs treated groups were significantly prolonged (P < .05). CsA, MMF, and AS-ODNs inhibited MD-1 expression and lymphocyte proliferation, as well as decreased serum level of IL-2 and increased that of IL-10; FK506, treatment showed all the effects mentioned above but up-regulated the IL-10 level; SRL had no significant influence on either MD-1 expression or IL-2 and IL-10 level, although it equally suppressed the proliferation (P < .05 vs controls). The negative correlation between MD-1 expression and lymphocyte proliferation or IL-2 level was significant, as was the positive correlation between it and IL-10 level (P < .01).

CONCLUSIONS

CsA, FK506, MMF, and AS-ODNs can efficiently inhibit MD-1 expression. The effects of the immunosuppressants are seemingly associated with the down-regulation of the IL-2 serum level. MD-1 was theorized to play an important role in rejection promotion, although the precise relationship between it and allograft survival still remains ambiguous.

Silencing T-bet defines a critical role in the differentiation of autoreactive T lymphocytes

As a means of developing therapies that target the pathogenic T cells in multiple sclerosis (MS) without compromising the immune system or eliciting systemic side effects, we investigated the use of T-bet-specific antisense oligonucleotides and small interfering RNAs (siRNA) to silence T-bet expression in autoreactive encephalitogenic T cells and evaluated the biological consequences of this suppression in experimental autoimmune encephalomyelitis, a model for MS. The T-bet-specific AS oligonucleotide and siRNA suppressed T-bet expression, IFNgamma production, and STAT1 levels during antigen-specific T cell differentiation. In vitro suppression of T-bet during differentiation of myelin-specific T cells and in vivo administration of a T-bet-specific antisense oligonucleotide or siRNA inhibited disease. T-bet was shown to bind the IFNgamma and STAT1 promoters, but did not regulate the IL-12/STAT4 pathway. Since T-bet regulates IFNgamma production in CD4(+) T cells, but to a lesser extent in most other IFNgamma-producing cells, T-bet may be a target for therapeutics for Th1-mediated diseases.

Ecology of Danger-dependent Cytokine-boosted Spontaneous Abortion in the CBA × DBA/2 Mouse Model. I. Synergistic Effect of LPS and (TNF-α + IFN-γ) on Pregnancy Loss

PROBLEM

Previous data have shown "danger" signals, such as bacterial lipopolysaccharide (LPS) acting via toll-like (tlr) receptors are required for early pregnancy failure in several murine abortion models. Indeed, the abortion rate increased in the CBA x DBA/2 model after a gestation day (gd) 7.5 injection of tumour necrosis factor (TNF)-alpha + interferon (IFN)-gamma only if the LPS-tlr signalling pathway was intact. High rates of cytokine-boosted abortion >80% loss can be achieved in certain animal colonies, that have a high endogenous (spontaneous) rate of resorption (30-50%). A specific role for LPS has been postulated to determine both the endogenous and cytokine-boosted losses.

METHODS

To test the role of LPS in spontaneous and cytokine-boosted abortions, recombinant TNF-alpha + IFN-gamma, and LPS were injected in different doses and sequences intraperitoneally (i.p.) into CBA x DBA/2 mated mice in the Toronto General Research Institute animal facility where the endogenous abortion rate is <30%. The effects of poly IC, a tlr3 agonist that induces IFN-gamma that can reverse LPS-induced tolerance, and effects of anti-MD-1 on TNF-alpha induction by LPS, poly IC, CPG, or HSP in vitro were also examined.

RESULTS

A high endogenous rate of loss similar to that seen in Clamart could be achieved by increasing exposure to LPS on the morning after mating (gd 0.5). The magnitude by which the abortion rate could be increased by an i.p. injection of 2000 u TNF-alpha + 1000 u IFN-gamma on gd 7.5 was independent of the endogenous rate of loss, and could not be increased by doubling the dose. One microgram of LPS given on day 7.5 achieved a similar rate of loss, and if given with the cytokines, synergistically boosted the rate of loss to near Clamart rates. LPS given 1 day prior to the cytokines abrogated the cytokine effect, whereas LPS given day 0.5 had no significant effect on the response to day 7.5 cytokine injection. Blocking MD-1 inhibited TNF-alpha stimulation by poly IC, LPS, CPG, or HSP in vitro, and reduced abortion rates. Poly IC did not avert LPS-type tolerance effects in vivo.

CONCLUSIONS

High endogenous rates of abortion in the CBA x DBA/2 model may be explained by exposure to LPS at the time of mating. Increased rates of loss triggered by cytokines later in pregnancy may depend on increased absorption of LPS from intestinal flora.

Comparison of mixed lymphocytic reactions to both xenogenic murine and allogenic human lymphocytes

AIM: To compare the mixed lymphocyte reactions (MLR) of human lymphocytes response to xenogenic murine lymphocytes and the allogenic human lymphocytes in vitro.

METHODS: Xeno-and allo- MLRs were set up and cellular classification study of xeno- and allo- MLRs were performed.

RESULTS: Human T cells response to xeno-cells was weaker than to allo-cells (P<0.05). Cellular classification study indicted that it was mainly CD4+ T cell involved in both allo- and xeno-MLRs, the former through direct and indirect pathways and the latter through indirect pathway. In addition, CD8+ T cell was involved in the reaction as well.

CONCLUSION: Xeno-MLR is weaker than allo-MLR. Xenogenic cells can only stimulate T cells through indirect pathway. Both MLRs share similar requirements for APCs, and human CD4 T cells are the major response cells.