Preparation and functional properties of polyclonal and monoclonal antibodies to murine MD-1

Inflammatory responses increase secretion of MD-1 protein

Radioprotective 105 (RP105) is a type I transmembrane protein, which associates with a glycoprotein, MD-1. Monoclonal antibody (mAb)-mediated ligation of RP105/MD-1 robustly activates B cells. RP105/MD-1 is structurally similar to Toll-like receptor 4 (TLR4)/MD-2. B-cell responses to TLR2 and TLR4/MD-2 ligands are impaired in the absence of RP105 or MD-1. In addition to RP105/MD-1, MD-1 alone is secreted. The structure of MD-1 shows that MD-1 has a hydrophobic cavity that directly binds to phospholipids. Little is known, however, about a ligand for MD-1 and the role of MD-1 in vivo To study the role of RP105/MD-1 and MD-1 alone, specific mAbs against MD-1 are needed. Here, we report the establishment and characterization of two anti-MD-1 mAbs (JR2G9, JR7G1). JR2G9 detects soluble MD-1, whereas JR7G1 binds both soluble MD-1 and the cell surface RP105/MD-1 complex. With these mAbs, soluble MD-1 was detected in the serum and urine. The MD-1 concentration was altered by infection, diet and reperfusion injury. Serum MD-1 was rapidly elevated by TLR ligand injection in mice. The quantitative PCR and supernatant-precipitated data indicate that macrophages are one of the sources of serum soluble MD-1. These results suggest that soluble MD-1 is a valuable biomarker for inflammatory diseases.

Functional characterization of a first avian cytochrome P450 of the CYP2D subfamily (CYP2D49)

The CYP2D family members are instrumental in the metabolism of 20-25% of commonly prescribed drugs. Although many CYP2D isoforms have been well characterized in other animal models, research concerning the chicken CYP2Ds is limited. In this study, a cDNA encoding a novel CYP2D enzyme (CYP2D49) was cloned from the chicken liver for the first time. The CYP2D49 cDNA contained an open reading frame of 502 amino acids that shared 52%-57% identities with other CYP2Ds. The gene structure and neighboring genes of CYP2D49 are conserved and similar to those of human CYP2D6. Additionally, similar to human CYP2D6, CYP2D49 is un-inducible in the liver and expressed predominantly in the liver, kidney and small intestine, with detectable levels in several other tissues. Metabolic assays of the CYP2D49 protein heterologously expressed in E. coli and Hela cells indicated that CYP2D49 metabolized the human CYP2D6 substrate, bufuralol, but not debrisoquine. Moreover, quinidine, a potent inhibitor of human CYP2D6, only inhibited the bufuralol 1'-hydroxylation activity of CYP2D49 to a negligible degree. All these results indicated that CYP2D49 had functional characteristics similar to those of human CYP2D6 but measurably differed in the debrisoquine 4'-hydroxylation and quinidine inhibitory profile. Further structure-function investigations that employed site-directed mutagenesis and circular dichroism spectroscopy identified the importance of Val-126, Glu-222, Asp-306, Phe-486 and Phe-488 in keeping the enzymatic activity of CYP2D49 toward bufuralol as well as the importance of Asp-306, Phe-486 and Phe-488 in maintaining the conformation of CYP2D49 protein. The current study is only the first step in characterizing the metabolic mechanism of CYP2D49; further studies are still required.

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.

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.

Structure analysis and expressions of a novel tetratransmembrane protein, lysosoma-associated protein transmembrane 4 β associated with hepatocellular carcinoma

AIM: To analyze the structure and expressions of the protein encoded by an HCC-associated novel gene, lysosome-associated protein transmembrane 4 β (LAPTM4B).

METHODS: Primary structure and fundamental characteristics of LAPTM4B protein were analysed with bioinformatics. Expressions of LAPTM4B in HCC tissues and various cell lines were detected using polyclonal antibodies and Western blot.

RESULTS: LAPTM4B encoded two isoforms of proteins with molecular masses 35-ku and 24-ku, respectively. The expression level of LAPTM4B-35 protein in HCC tissues was dramatically upregulated and related to the differentiation status of HCC tissues, and it was also high in some cancer cell lines. Computer analysis showed LAPTM4B was an integral membrane protein with four transmembrane domains. LAPTM4B showed relatively high homology to LAPTM4A and LAPTM5 in various species.

CONCLUSION: LAPTM4B gene encoded two isoforms of tetratransmembrane proteins, LAPTM4B-35 and LAPTM4B-24. The expression of LAPTM4B-35 protein is upregulated and associated with poor differentiation in human HCC tissues, and also at high levels in some cancer cell lines. LAPTM4B is an original and conserved protein.

MD-1 is a critical part of the mechanism causing Th1-cytokine-triggered murine fetal loss syndrome

PROBLEM

Fetal loss syndrome (abortion/resorption) occurring on or after gestation day (gd) 9.5 in CBA/JxDBA/2 matings is dependent upon presence of TNF-alpha + IFN-gamma, which act by increasing expression of fg12 prothrombinase at the feto-maternal interface. The magnitude by which the abortion rate can be boosted by an injection of these cytokines on gd 7.5 depends on endogenous rate of loss, and appears to depend on microbial flora. Is cytokine-triggered abortion dependent upon a third signaling pathway that senses 'danger'?

METHODS

Female CBA/J were mated to DBA/2 males and, C57B1/6 and C57B1/6 TNFalphaR1-/-Mak were mated to C57B1/6 control or TNFalphaR1-/-Mak males. LPS from Escherichia coli and Salmonella enteritidis, or the combination of TNF-alpha + IFN-gamma, was injected to stimulate abortions. The effect of anti-MD-1, which interferes with expression of CD14 and, hence, with signaling by LPS via the CD14-tlr4 complex, on TNF-alpha + IFN-gamma was tested. The presence of MD-1 in the uterus was evaluated by in situ hybridization, and effect of lipopolysaccharide (LPS) on mice lacking TNF-alphaR1 was tested.

RESULTS

Anti-MD-1 completely abrogated TNF-alpha + IFN-gamma-induced abortions. MD-1 was expressed on trophoblast and in deciduas on gd 8.5 but LPS could not abort mice that lacked the type 1 receptor for TNF-alpha. Pregnant CBA/J females had classical resorptions (abortions) countable on gd 13.5-14.5 in response to LPS from E. coli or S. enteritidis, but C57B1/6 strain mice resorbed only in response to the latter, and E. coli LPS appeared to induce 'occult' losses. 'Occult' loss did not require TNF-alphaR1.

CONCLUSIONS

TNF-alpha + IFN-gamma could not induce murine abortions without co-presence of a 'danger' signal such as LPS acting via CD14 on toll receptors, and LPS could not act without co-signaling by TNF-alpha. Classical resorptions/abortions and 'occult' losses have a different mechanism in these models as reflected in type of endotoxin and requirement for TNF-alphaR1 signaling.

The same immunoregulatory molecules contribute to successful pregnancy and transplantation

PROBLEM

At least two dendritic cell-associated molecules have been shown to contribute to the successful outcome of organ and tissue allografts in mice, namely CD200 and MD-1. CD200 is up-regulated in rodent transplantation models where successful inhibition of rejection is accomplished, and is believed to signal immunosuppression following engagement of a receptor, CD200R, on macrophages and/or gammadelta T-cell receptor (gammadelta TCR+ cells MD-1 is implicated in controlling expression of costimulatory molecules including CD80/CD86 which induce an immunorejection response, and thus inhibition of MD-1 expression also facilitates increased graft survival MD-1 also stabilizes expression of CD14, part of the receptor complex for LPS. As well as the inhibition of rejection which follows blockade of MD-1 expression and/or augmentation of CD200 expression, an altered polarization in cytokine production is seen, with increased expression of interleukin-4 (IL-4), IL-10 and transforming growth factor-beta (TGF-beta), and decreased IL-2, interferon-gamma (IFN-gamma) and tumor nerosis factor-alpha (TNF-alpha). Successful pregnancy in allopregnant mice also depends upon control of graft rejection mechanisms. Proinflammatory T-helper 1 (Th1) cytokines (TNF-alpha + IFN-gamma + IL-1) have been shown to cause spontaneous abortion in mice by activating a novel prothrombinase, fibrinogen-like peptide (fibroleukin) fgl2, which may promote fibrin deposition in the graft rejection process; expression of IL-10, TGF-beta, and progesterone-induced blocking factor (PIBF) in contrast leads to lowering of abortion rates. Interestingly, the spontaneous abortion rates in abortion-prone CBA x DBA/2 matings and in the low abortion rate CBA x BALB/c matings were lower than the frequency of implantation sites showing fibrin(hi) + fgl2 (mRNA)hi, implying regulation of the pro-abortion consequences of fgl2 expression.

METHODS

We have investigated, by in situ hybridization, CD200, MD-1 and fgl2 expression in implantation sites in different strains of mice, and studied the effects of anti-MD-1, anti-CD200 and CD200Fc immunoadhesin on fetal and allograft survival. The role of indoleamine dioxygenase (IDO) was evaluated.

RESULTS

CD200 mRNA expression occurred in the same sites as fgl2 mRNA. Anti-CD200 antibody raised the abortion rate to predicted levels, and infusion of a CD200 immunoadhesin reduced the abortion rate, as did an anti-MD-1 antibody. The latter also improved organ and tissue graft survival. Suppression by antigen-presenting macrophages triggered by CD200 is dependent upon intact IDO activity.

CONCLUSION

Regulation of CD200 and MD-1 expression may control both pregnancy and allograft survival.

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

BACKGROUND

Altered expression of murine MD-1, a molecule controlling expression of members of the interleukin (IL)-1 receptor family of signaling proteins, regulates antigen-presenting cell-induced alloreactions. We investigated the effect of treatment with antisense deoxyoligonucleotides or antibodies to MD-1 in vivo on allogeneic and xenogeneic skin graft survival and the immune responses in transplanted mice.

METHODS

C3H mice received C57BL/6 or Lewis rat skin grafts, followed by i.v. injections of anti-MD-1 antibody or antisense oligonucleotides or control reagents at 48-hr intervals. Survival was monitored. In separate studies, mice were sacrificed at 5-day intervals. Serum was analyzed for circulating MD-1 antigen, and peritoneal cells for surface expression of MD-1. The proliferative and cytolytic response of lymphocytes harvested from treated animals and restimulated in vitro with allo- or xenogeneic cells, and the cytokines produced, was measured. Graft histology was assessed at 11 days after transplantation.

RESULTS

Treatment with anti-MD-1 oligonucleotides or antibodies suppressed rejection of both xeno- and allogeneic grafts, decreased induction of graft-specific cytotoxic T cells, increased production of type-2 cytokines (IL-4 and IL-10), and decreased production of type-1 cytokines (IL-2 and interferon-gamma). Serum levels of MD-1 were suppressed, as was expression of MD-1 on the surface of antigen-presenting cells. Grafts from MD-1-treated mice showed little lymphocyte infiltration, and no signs of graft necrosis.

CONCLUSION

Our data suggest a critical in vivo role for MD-1 expression in regulating graft rejection, as well as in the concomitant sensitization of T cells and their cytokine production profile, which parallels the rejection response.

Thinking outside the box: mechanisms of environmental selective pressures on the outcome of the materno-fetal relationship

PROBLEM

Study of mechanisms causing spontaneous abortion of the vascularized placenta have focused primarily on the feto-maternal immunological relationship within the pregnant mother. The Th1 cytokines such as tumor necrosis factor (TNF)-alpha + interferon (IFN)-gamma derived in part from natural killer (NK) and NKgammadeltaT cells have been implicated in causing abortion via up-regulation of the novel prothrombinase fgl2 at the feto-maternal interface; Th2/3 cytokines such as interleukin (IL)-10, progesterone-induced blocking factor (PIBF), and TGF-beta2 derived from gammadeltaT cells stimulated by embryo antigens in the context of the OX-2 (CD200) tolerance signal have been viewed as counteracting the Th1 effect. These mechanisms are distinct from those causing and preventing occult pregnancy loss during the periimplantation phase of pregnancy prior to development of a vascularized placenta. Spontaneous abortions in the CBA/J x DBA/2 can be boosted by injecting TNF-alpha + IFN-gamma, but the boosted abortion rates can range from < or = 30 to > 80%, depending on the loss rate in uninjected mice, and this is not explainable by the endogenous level of these cytokines. Furthermore, there is a poor correlation between Th1/Th2.3 cytokine ratios and abortion rates. Could there be a third factor involved, and if so, what might this mean?

METHODS

Known precipitants of recurrent abortion in mice were reviewed with particular attention to stress and endotoxin absorption. The effect of antagonizing the response to bacterial lipopolysaccharide (LPS) (endotoxin) was tested. Data on environmental selective pressures were considered (i.e. thinking outside the 'box', which typifies the conventional approach to thinking about materno-fetal interactions).

RESULTS

Th1 cytokine-triggered abortions appear to depend on availability/presence of LPS.

CONCLUSIONS

Environmental selective pressures are implicated in eliminating 'genetically weaker' embryos in early pregnancy.