Transplant tolerance modifying antibody to CD200 receptor, but not CD200, alters cytokine production profile from stimulated macrophages

Increased C57BL/6 allograft survival following donor-specific dendritic cell (DC) portal vein (pv) pre-transplant immunization of C3H mice is associated with increased expression of the molecule CD200 on DC, delivery of suppressive signals by CD200(r+) macrophages, and polarization in cytokine production towards type-2 cytokines. Infusion of anti-mouse CD200 monoclonal antibody abolishes these effects. We have used whole Ig, and F(ab')(2) fragments, of anti-CD200 and anti-CD200(r) mAb to explore the relative signaling role of CD200(+) versus CD200(r+) cells in suppression of type-1 cytokine production in mixed leukocyte cultures (MLC), and enhanced graft survival in vivo. Simple neutralization of CD200 [even by F(ab')(2) antibody] reversed CD200-mediated suppression. However, only whole anti-CD200(r) antibody was effective in stimulating suppression from CD200(r+) cells. Suppression of cytokine induction following cross-linking of CD200(r+) cells in vitro was attenuated by anti-IL-6 mAb. Our data are consistent with the hypothesis that CD200(r) itself delivers the crucial intracellular signal leading to immunosuppression, a feature likely of importance in autoimmunity and transplantation.

Procoagulants in fetus rejection: the role of the OX-2 (CD200) tolerance signal

The spontaneous loss of normal karyotype embryos may be initiated or prevented by the maternal immune system. In mice, loss between the time of implantation (day 4.5) and formation of a vascularized placenta (day 9.5) when the embryo is too large to survive by diffusion alone, is analogous to occult pregnancy failure in humans. They are called occult because usually the woman does not know she is pregnant. From studies in mice, these early losses have a different mechanism than abortion of a vascularized placenta (analogous to clinically evident human spontaneous miscarriage). The latter depend on the activation of the novel prothrombinase fgl2 on the fetal trophoblast and in maternal decidua by the T helper-1 (Th1) type cytokines TNF- alpha+gamma -interferon that arise from NK cells and NK gammadelta T cells; conversion of prothrombin to thrombin which in turn generates IL8 that activates polymorphonuclear leukocytes leads to embryonic death. These inflammatory processes are counteracted by Th2/3-type cytokines that arise in part from V gamma 1 delta 6 T cells reacting to, as yet, unidentified trophoblast antigens in the presence of the 'tolerance signaling molecule' OX-2. By contrast, peri-implantation losses (between implantation and formation of a vascularized placenta, analogous to occult losses in humans) appear to be dependent upon perforin(+)cells, complement activation, and products of alphabeta T and NK alphabeta T cells, but not on TNF- alpha or procoagulant activation. Similarities and differences between findings in the mouse and human, and the potential evolutionary significance of mechanisms affecting reproductive success are reviewed.

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

Rabbits, rats and hamsters were immunized with KLH-coupled synthetic peptide sequences of the murine MD-1 molecule. Serum from immunized animals bound in Western gels to a 25 KDa protein extracted from LPS stimulated mouse spleen cells, as did a rat hybridoma (SH1.2.47) prepared from peptide-immunized rats. CHO cells transfected with a plasmid cDNA construct encoding murine MD-1, the target antigen for the antibodies in question, were also stained (in FACS) by the same antibodies. Patching and capping of the antigen(s) detected by any one of these sera abolished binding of all antibodies in subsequent FACS analysis, consistent with the hypothesis that they all detected the same antigen. In a final study to assess the possible involvement of MD-1 in regulation of cell activation for cytokine production following allostimulation, we found that all of the antibodies inhibited IL-2 and IFNgamma production, while enhancing IL-4 and IL-10 production, in mixed leukocyte reactions (MLR) in vitro.

Role of cytokines in allograft rejection

This review examines the evidence, both from experimental models and numerous clinical settings, that has suggested that suppression of acute allograft rejection correlates with a relative decrease in type-1 cytokine production and an increase in type-2 cytokine production. This correlation has spurred studies on cytokine gene polymorphisms, to assess evidence that certain cytokine-producing genotypes are associated with increased incidence of transplant rejection, and also an interest in the value of monitoring cytokine profiles post-transplantation in long-term follow-up of transplant patients. An appraisal is given of the potential for cytokine gene therapy in transplantation, using both dendritic cells (DC) and graft tissue itself as target cells. Along the same lines, gene-targeting of DCs to increase or decrease expression of molecules (CD40/CD80/CD86/CD200) believed to control the polarization of T cell development (and cytokine production) is discussed. The review concludes with consideration of the possibility that one future goal of the pharmaceutical industry will be to develop novel immunosuppressants with selective inhibitory action on the production of distinct cytokines.

Role of CTLA 4-Ig on induction of unresponsiveness to multiple minor alloantigens

LPS blasts inhibited graft rejection in multiple minor incompatible strain combinations but not in presensitized animals or in major histoincompatible combinations.

Fgl2 prothrombinase expression in mouse trophoblast and decidua triggers abortion but may be countered by OX-2

Spontaneous abortion of normal karyotype embryos in mice and in humans is associated with an increase in uterine T helper (Th) 1 type proinflammatory cytokines, tumour necrosis factor (TNF)-alpha, interferon-gamma and interleukin (IL)-1, and a deficiency of Th2/3 type cytokines, IL-4, IL-10, and transforming growth factor (TGF)-beta2. In mice, Th1 cytokines up-regulate a novel prothrombinase, fgl2, which via thrombin, leads to activation of polymorphonuclear leukocytes that terminate the pregnancy. Here we show that Th1 cytokines up-regulate fgl2 mRNA in fetal trophoblast and secondary decidua of CBA/JxDBA/2 and CBA/JxBALB/c matings, and promote fibrin deposition. This pattern is accompanied by a high rate of abortion. However, the spontaneous abortion rates in abortion-prone CBAxDBA/2 matings and in low abortion rate CBAxBALB/c matings were significantly lower than that expected from the frequency of implantations with high levels of fibrin and fgl2 mRNA(hi). As the glycoprotein OX-2 occurs in the pregnant rat uterus and can deviate cytokine responses to Th2/3, we investigated OX-2 in pregnant CBA/J mice. We found OX-2 mRNA was present at the same sites as fgl2 mRNA, but was reduced in response to Th1 cytokines. Furthermore, anti-OX-2 raised the abortion rate to predicted levels, while recombinant OX-2 dramatically reduced the abortion rate. Fgl2 prothrombinase may provide a mechanism explaining pregnancy loss, and conversely, successful pregnancy may be due in part to OX-2-dependent activation of maternal tolerance mechanisms at the feto-maternal interface.

Receptor engagement on cells expressing a ligand for the tolerance-inducing molecule OX2 induces an immunoregulatory population that inhibits alloreactivity in vitro and in vivo

Increased survival of C57BL/6 renal allografts following portal vein donor-specific pretransplant immunization of C3H mice is associated with increased expression of the molecule OX2 seen on host dendritic cells, along with a marked polarization in cytokine production from lymphocytes harvested from the transplanted animals, with preferential production of IL-4, IL-10, and TGF-beta on donor-specific restimulation in vitro, and decreased production of IL-2, IFN-gamma, and TNF-alpha compared with non-portal vein-immunized control transplanted mice. The increased renal allograft survival and the altered cytokine production are abolished by infusion of anti-mouse OX2 mAb (3B6). Infusion of a soluble OX2:Fc immunoadhesin can itself produce significant prolongation of xeno- and allografts in mice. We have used FITC-conjugated OX2:Fc to characterize cells expressing a ligand (OX2L) for OX2, and provide evidence that subpopulations of LPS-stimulated splenic macrophages, Con A-activated splenic T cells, and the majority (>80%) of gammadeltaTCR(+) T cells express this ligand. We show below that F4/80(+), OX2L(+) splenic macrophages, admixed with OX2:Fc, represent a potent immunosuppressive population capable of causing more profound inhibition of alloreactivity in vitro or in vivo than that seen using either OX2:Fc or OX2(+) (or OX2L(+)) cells alone. Immunoregulation by this OX2L(+) population occurs in an MHC-restricted fashion.

Serum cytokine values and fatigue in chronic hepatitis C infection

Patients with chronic hepatitis C infection often experience fatigue. In many clinical situations, an association between fatigue and altered serum cytokine levels has been found. Altered cytokine levels in patients with hepatitis C have not shown a correlation with the degree of serum transaminase elevation or pathological change on liver biopsy. The aim of our study was to examine whether there was an association between abnormal serum cytokine levels and fatigue in patients with compensated chronic hepatitis C. Patients referred to a tertiary care hepatology clinic who were hepatitis C antibody positive and who had elevated alanine aminotransferase (ALT) levels were eligible for entry into the study. A control group was also included. Subjects in both groups who had characteristics other than hepatitis C that were known to alter cytokine values and/or cause fatigue were excluded. Patients completed a validated questionnaire to determine their fatigue severity score (FSS). Bioassays were used to measure interleukin (IL)-1, IL-6 and tumour necrosis factor-alpha (TNF-alpha) levels in early morning serum samples taken from patients and controls. Altered cytokine values were defined as those more than two standard deviations above the mean control value. Data was analysed using SPSS, version 8.01. Of the 78 patients with chronic hepatitis C who participated in the study, 19 (24%), 24 (30%) and 45 (56%) had elevated levels of IL-1, IL-6 and TNF-alpha, respectively, compared with only two (6%) of the control group who had elevation of any of the three cytokines. No correlation was found between the FSS and serum cytokine levels, when analysed singly or in combination, in patients with chronic hepatitis C. Hence, alteration in early morning serum levels of IL-1, IL-6 and TNF-alpha in patients with chronic hepatitis C infection and elevated ALT levels bear no correlation with the symptom of fatigue.

Evidence for persistent expression of OX2 as a necessary component of prolonged renal allograft survival following portal vein immunization

Following portal vein (pv) pretransplant immunization of C3H mice, there is an early (within 2 days) increase in expression of the molecule OX2 seen on host dendritic cells (DC), along with increased survival of C57BL/6 renal allografts transplanted within 24 h of pv immunization. In addition, there is a marked polarization in cytokine production from lymphocytes harvested from the transplanted animals, with preferential production of IL-4, IL-10, and TGFbeta on donor-specific restimulation in vitro, and decreased production of IL-2, IFN-gamma, and TNFalpha compared with non-pv-immunized control transplanted mice. Both the increased renal allograft survival and the altered cytokine production are abolished by infusion of anti-mouse OX2 monoclonal antibody (3B6), even when antibody infusion is begun as late as 10 days following transplantation. Quantitative PCR analysis independently shows that OX2 expression is increased in the spleen and liver of transplanted mice as late as 21 days following pv immunization. In vitro studies with an OX2:Fc immunoadhesion had suggested that immunosuppression induced by this soluble form of the OX2 molecule was dependent primarily upon an early (OX2-dependent) signal. This discrepancy between in vivo and in vitro data possibly reflects a role for OX2 in the in vivo recruitment of other (immunregulatory) cells. Consistent with this hypothesis, regardless of the time (posttransplantation) of in vivo infusion of anti-OX2 antibody, within 2 days we observed a decline in the functional activity of a previously characterized immunoregulatory gammadeltaTCR(+) cell population, which can be monitored by its ability to regulate cytokine production in vitro.

Functional human T-cell immunity and osteoprotegerin ligand control alveolar bone destruction in periodontal infection

Periodontitis, a prime cause of tooth loss in humans, is implicated in the increased risk of systemic diseases such as heart failure, stroke, and bacterial pneumonia. The mechanisms by which periodontitis and antibacterial immunity lead to alveolar bone and tooth loss are poorly understood. To study the human immune response to specific periodontal infections, we transplanted human peripheral blood lymphocytes (HuPBLs) from periodontitis patients into NOD/SCID mice. Oral challenge of HuPBL-NOD/SCID mice with Actinobacillus actinomycetemcomitans, a well-known Gram-negative anaerobic microorganism that causes human periodontitis, activates human CD4(+) T cells in the periodontium and triggers local alveolar bone destruction. Human CD4(+) T cells, but not CD8(+) T cells or B cells, are identified as essential mediators of alveolar bone destruction. Stimulation of CD4(+) T cells by A. actinomycetemcomitans induces production of osteoprotegerin ligand (OPG-L), a key modulator of osteoclastogenesis and osteoclast activation. In vivo inhibition of OPG-L function with the decoy receptor OPG diminishes alveolar bone destruction and reduces the number of periodontal osteoclasts after microbial challenge. These data imply that the molecular explanation for alveolar bone destruction observed in periodontal infections is mediated by microorganism-triggered induction of OPG-L expression on CD4(+) T cells and the consequent activation of osteoclasts. Inhibition of OPG-L may thus have therapeutic value to prevent alveolar bone and/or tooth loss in human periodontitis.

Detection of host and donor cells in sex-mismatched rat nerve allografts using RT-PCR for a Y chromosome (H-Y) marker

The donor and host source of support cells, such as Schwann cells, in nerve allograft segments have been the subject of debate. The objective of the present study was to assess the utility of a molecular technique that probes for a Y chromosome expressed gene (H-Y) in distinguishing host from donor tissue in sex-mismatched nerve allograft segments. Forty-two Lewis rats received bilateral syngeneic Lewis or allogeneic ACI rat peroneal nerve grafts, with or without cyclosporin A (CsA) treatment. At different times thereafter animals were sacrificed and samples were harvested. We transplanted males and females reciprocally, to study both survival of donor cells (persisting H-Y mRNA in male grafts by transcription polymerase chain reaction (RT-PCR), and graft infiltration by host cells (detectable H-Y mRNA in female grafts). A kinetic analysis revealed a progressive loss of viable donor cells (loss of H-Y mRNA signal) from allografts, beginning 2-3 weeks, and culminating at 4 weeks, with little detectable H-Y in the absence of CsA treatment. CsA treatment led to prolonged survival of allograft cells, confirmed by detectable H-Y mRNA. By studying female grafts in male rats we could confirm that loss of viable donor tissue in allografts was accompanied by infiltration of host (H-Y mRNA positive) cells, whereas no H-Y mRNA signal was seen in males receiving autografts from females or in immunosuppressed allograft segments. These data suggest that reverse RT-PCR analysis for a Y chromosome gene product can be a valuable tool to assess the origin of viable cells in sex-mismatched nerve allotransplantation tissue.

Regulation of gene expression of murine MD-1 regulates subsequent T cell activation and cytokine production

The immunoadhesin (OX2:Fc) comprising the extracellular domain of murine OX2 linked to IgG2aFc, inhibits production of IL-2 and IFN-gamma by activated T cells and increases allograft and xenograft survival in vivo. Increased expression of OX2 on dendritic cells (DC) in vivo following preimmunization via the portal vein is also associated with elevated expression of MD-1. We have used antisense oligodeoxynucleotides (ODNs) to MD-1 to investigate the effect of inhibition of expression of MD-1 by DC on their function as allostimulatory cells. We also investigated by FACS analysis the cell surface expression of OX2, CD80, and CD86 on DC incubated with ODN-1 blocking MD-1 expression. Blocking MD-1 gene expression inhibits surface expression of CD80 and CD86, but not of OX2. DC incubated with ODN-1 to MD-1 did not stimulate IL-2 or IFN-gamma production, but generated cells able to suppress, in a second culture of fresh DC plus allogeneic T cells, production of IL-2 and IFN-gamma. This inhibition was blocked by anti-OX2 mAb. Infusion of DC preincubated with ODN-1 prolonged renal allograft survival, an effect also reversed by anti-OX2 mAb. By FACS, incubation of DC with anti-MD-1 Ab to promote capping eliminated cell surface expression of MD-1 and CD14 without altering DEC205, DC26, CD80, CD86, or OX2 expression. Thus OX2 and MD-1 are independent surface molecules on DC that may reciprocally regulate T cell stimulation. MD-1 is linked to CD14, a "danger receptor complex," and activation of this complex can regulate cell surface expression of CD80/CD86, which signal T cells.

Synergy in induction of increased renal allograft survival after portal vein infusion of dendritic cells transduced to express TGFbeta and IL-10, along with administration of CHO cells expressing the regulatory molecule OX-2

Dendritic cells (DC), generated from C57BL/6 mouse bone marrow cells cultured with GM-CSF and IL-4 for 9 days, were engineered to express constitutively the cytokines TGFbeta, IL-10, and IL-12, using adenovirus vectors constructed using an E1-deleted replication-deficient recombinant adenovirus carrying the appropriate cDNA for the relevant cytokines (Ad-TGFbeta, Ad-IL-12, or Ad-IL-10). C3H mice receiving nontransduced DC or pretransplant infusion of DC-Ad-LacZ showed increased survival of C57BL/6 renal grafts relative to that of control nonimmunized mice. Transfusion of Ad-IL-12-transduced DC abolished this increased survival, leading to a graft survival equivalent to that of controls with no DC. Optimal graft survival was seen in the group receiving a mixture of DC transduced with constructs for both IL-10 and TGFbeta. There was a correlation between increased graft survival and both inhibition of the induction of CTL and enhancement of a polarization to produce type-2 cytokines (IL-4, IL-10, and TGFbeta) on antigen-specific restimulation in vitro. These effects were more pronounced following concomitant infusion of CHO cells transfected with a full-length cDNA for murine OX-2.

Alterations in chemokine mRNA expression in animals receiving portal vein immunization and renal allo- or xenotransplantation precede altered cytokine production

We have analyzed chemokine mRNA expression in graft tissue of C3H/HEJ mice receiving allogeneic (C57BL/6) or xenogeneic [Lewis (LEW) rat donors] kidney grafts and correlated this with graft survival. Since donor-specific portal vein (pv) immunization is known to increase allo- and xenograft survival, in some cases recipients also received pretransplant pv or intravenous (iv) immunization; other animals received the antioxidant N-acetylcysteine (NAc) to examine the role of ischemia/reperfusion injury in the changes observed. Graft tissue and lymph nodes draining the respective grafts were obtained at various times posttransplantation and used for quantitative polymerase chain reaction analysis of mRNAs for different chemokines. In addition, lymphocytes were restimulated in culture with donor antigen and supernatants assayed for different cytokines. We observed that early increases in mRNA for MCP-1 preceded a polarization to type 2 cytokine production. Infusion of NAc twice daily for 4 days following transplantation further altered chemokine mRNA expression (increased MCP-1 and RANTES; decreased CINC); led to more enhanced type 2 cytokine production relative to control animals; and further increased xenograft survival. By use of heteroantibodies to different chemokines, anti-MCP-1 alone, but not antibodies to MIP-1alpha or RANTES, abolished this early polarization in cytokine production, implying a causal link between MCP-1 production and polarization in cytokine production. We conclude that manipulation of chemokine production early after transplantation might indirectly modify graft outcome by modifying cytokine production.

An immunoadhesin incorporating the molecule OX-2 is a potent immunosuppressant that prolongs allo- and xenograft survival

We have established that, in mice receiving donor-specific immunization by the portal vein, the increased graft survival seen is associated with the increased expression of a molecule (OX-2) on a subpopulation of dendritic cells (DC), and polarization of cytokine production to type 2 cytokines on Ag-specific restimulation of cells from these mice. Furthermore, infusion of a mAb to OX-2 blocks both the increased graft survival and the altered cytokine production seen. We have constructed an immunoadhesin in which the extracellular domain of OX-2 is linked to the murine IgG2a Fc region, and we have expressed this molecule (OX-2:Fc) in a eukaryotic (baculovirus) expression system. Incubation of lymphocytes with 50 ng/ml OX-2:Fc inhibits a primary mixed lymphocyte reaction in vitro, as assayed by proliferation and induction of cytotoxic T cells, and also alters cytokine production with decreased IL-2 (IFN-gamma) production and increased IL-4 (IL-10) production. Similarly, in vivo infusion of OX-2:Fc promotes increased allo- and xenograft (both skin and renal grafts) survival and decreases the Ab response to sheep erythrocytes. Our data suggest this molecule might have clinical importance in allo- and xenotransplantation.

Evidence for epitope spreading and active suppression in skin graft tolerance after donor-specific transfusion

BACKGROUND

To clarify the controversial results in the literature regarding the role of donor-specific transfusion (DST) on allograft survival, we have examined the influence of the following on DST-induced allograft survival in a 2C transgenic mouse model: varying the time between DST and transplantation; the role of MHC disparities between donor and recipient; whether tolerance induced by DST spreads to skin allografts expressing other alloantigens; and whether cyclosporine (CsA) treatment could further modulate skin allograft tolerance after DST.

METHODS AND RESULTS

The studies were performed in both 2C anti-Ld (MHC class I) transgenic and normal (nontransgenic) mice. Our data demonstrate that a single infusion of Ld-mismatched lymphocytes 7 days before transplantation leads to permanent acceptance of donor-specific skin allografts in both transgenic (58/58) and nontransgenic (8/8) mice in the absence of any other nonspecific immunosuppressive treatment. Pretransplantation DST from donors mismatched for more than one MHC antigen (Ag) has no beneficial effect on subsequent donor skin allograft survival. However, Ld plus multiple minor histocompatibility (mH) Ag-mismatched DST induced permanent acceptance of donor-specific skin allografts. Tolerance induced by one-locus Ld-mismatched DST spreads to skin allografts expressing either two-locus Ld or one-locus Ld plus multiple mH Ags. Administration of CsA after DST diminished skin allograft survival, rather than enhancing it, suggesting that tolerance in this model system is established by an active immunological process sensitive to CsA.

CONCLUSIONS

(1) Pretransplantation infusion of Ld-mismatched lymphocytes in the presence or absence of multiple mH mismatches induces permanent survival of donor-specific skin allografts. (2) CsA abrogates DST-induced transplantation tolerance.

Preparation and functional properties of monoclonal antibodies to human, mouse and rat OX-2

We have prepared mouse and rat hybridomas to a 43-kDa molecule expressed in the thymus, on a subpopulation of dendritic cells, and in the brain, in mammalian tissue derived from mouse, rat and human. Using CHO cells transiently transfected with adenovirus vector(s) expressing a cDNA construct for the relevant OX-2 gene, we show these monoclonal antibodies (Mabs) detect a molecule encoded by this construct (rat OX-2 (rOX-2), mouse OX-2 (mOX-2) and human OX-2 (huOX-2), respectively). Furthermore, at least some of the anti-rat Mabs detect determinants expressed on the murine OX-2 molecule, as we predicted in an earlier publication. Previous studies have implied that this molecule might serve an important role in regulation of cell signaling for cytokine production. Using one-way mixed leukocyte reactions we show that when cells are cultured in the presence of the species-specific Mab, cytokine production becomes polarized 'away from' type-2 cytokine production, with preferentially increased expression of type-1 cytokine production.

Effect of interleukin-6 secreted by engineered human stromal cells on osteoclasts in human bone

The effect of elevated human IL-6 (hIL-6) production by human bone marrow (Hu-BM) stromal cells on osteoclasts in human bone was examined. Human bone was implanted into nonobese diabetic mice with severe combined immunodeficiency (Hu-Bone-NOD/SCID mice). Immunohistochemistry of bone implants and mouse spleens (at 20 weeks), showed human CD45+ cells, B cells, and macrophages in both tissues. Thus, Hu-BM cells survive human bone transplantation and infiltrate mouse tissue. Bone implants had 75 +/- 12% (mean +/- SD) human CD45+ cells, and 9 +/- 4% mouse hematopoietic cells. A retrovirus vector containing the human IL-6 gene was used to transduce Hu-BM stromal cells (IL-6/stromal) and the PA317 cell line (IL-6/PA317). IL-6/ stromal cells (secreting, on average, 17 microg of hIL-6/10(6) cells per 24 h) were injected directly into human bone implants in Hu-Bone-NOD/SCID mice. IL-6/PA317 cells (secreting 16 microg/mL of hIL-6/10(6) cells per 24 h) were injected intraperitoneally into Hu-Bone-NOD/SCID mice. Analyses of sera from both groups of animals showed elevated levels of IL-6. However, only bone implants engrafted with IL-6/stromal cells had a statistically significant increase in osteoclast-lined mineralized trabecular bone surface (BS). Thus, a high concentration of serum hIL-6 in Hu-Bone-NOD/SCID mice alone does not increase osteoclast-lined BS in bone implants. Most importantly, it is the type of human BM cell that secretes the high levels of hIL-6 that is most critical.

Evidence That an OX-2-Positive Cell Can Inhibit the Stimulation of Type 1 Cytokine Production by Bone Marrow-Derived B7-1 (and B7-2)-Positive Dendritic Cells

We reported that hepatic mononuclear, nonparenchymal cells (NPC) can inhibit the immune response seen when allogeneic C57BL/6 dendritic cells (DC) are incubated with C3H spleen responder cells. Cells derived from these cultures transfer increased survival of C57BL/6 renal allografts in C3H mice. We also found that increased expression of OX-2 on DC was associated with inhibition of cytokine production and renal allograft rejection. We explored whether inhibition by hepatic NPC was a function of OX-2 expression by these cells. Fresh C57BL/6 spleen-derived DC were cultured with C3H spleen responder cells and other putative coregulatory cells. The latter were derived from fresh C3H or C57BL/6 liver NPC, or from C3H or C57BL/6 mice treated for 10 days by i.v. infusion of human Flt3 ligand. Different populations of murine bone marrow-derived DC from cultures of bone marrow with IL-4 plus granulocyte-macrophage-CSF were also used as a source of putative regulator cells. Supernatants of all stimulated cultures were examined for functional expression of different cytokines (IL-2, IL-4, IFN-γ, and TGFβ). We found that fresh C57BL/6 splenic DC induced IL-2, not IL-4, production. Cells from the sources indicated inhibited IL-2 and IFN-γ production and promoted IL-4 and TGFβ production. Inhibition was associated with increased expression of OX-2 on these cells, as defined by semiquantitative PCR and FACS analysis. By size fractionation, cells expressing OX-2 were a subpopulation of NLDC145+ cells. Our data imply a role for cells expressing OX-2 in the regulation of induction of cytokine production by conventional allostimulatory DC.

Evidence that an OX-2-positive cell can inhibit the stimulation of type 1 cytokine production by bone marrow-derived B7-1 (and B7-2)-positive dendritic cells

We reported that hepatic mononuclear, nonparenchymal cells (NPC) can inhibit the immune response seen when allogeneic C57BL/6 dendritic cells (DC) are incubated with C3H spleen responder cells. Cells derived from these cultures transfer increased survival of C57BL/6 renal allografts in C3H mice. We also found that increased expression of OX-2 on DC was associated with inhibition of cytokine production and renal allograft rejection. We explored whether inhibition by hepatic NPC was a function of OX-2 expression by these cells. Fresh C57BL/6 spleen-derived DC were cultured with C3H spleen responder cells and other putative coregulatory cells. The latter were derived from fresh C3H or C57BL/6 liver NPC, or from C3H or C57BL/6 mice treated for 10 days by i.v. infusion of human Flt3 ligand. Different populations of murine bone marrow-derived DC from cultures of bone marrow with IL-4 plus granulocyte-macrophage-CSF were also used as a source of putative regulator cells. Supernatants of all stimulated cultures were examined for functional expression of different cytokines (IL-2, IL-4, IFN-gamma, and TGFbeta). We found that fresh C57BL/6 splenic DC induced IL-2, not IL-4, production. Cells from the sources indicated inhibited IL-2 and IFN-gamma production and promoted IL-4 and TGFbeta production. Inhibition was associated with increased expression of OX-2 on these cells, as defined by semiquantitative PCR and FACS analysis. By size fractionation, cells expressing OX-2 were a subpopulation of NLDC145+ cells. Our data imply a role for cells expressing OX-2 in the regulation of induction of cytokine production by conventional allostimulatory DC.

TCR diversity in gammadeltaTCR+ hybridomas derived from mice given portal vein donor-specific pre-immunization and skin allografts

Portal venous (p.v.) immunization with multiple minor histoincompatible cells leads to antigen-specific increased skin allograft survival. GammadeltaTCR+ hybridoma cells, prepared from mesenteric lymphocytes of p.v. immunized animals, can adoptively transfer this increased graft survival to naive animals. We have analyzed VgammaVdelta gene usage, and TCR gamma-chain junctional diversity in gammadeltaTCR+ hybridomas from mice immunized with different antigen combinations by p.v. or conventional lateral tail vein (i.v.) immunization. Following p.v. immunization two independent sets of hybridoma cells were derived, one expressing a common gamma-chain junctional sequence which was also found in > 85% of the hybridomas derived following i.v. immunization, while the other set showed remarkable gamma-chain junctional sequence diversity. The diversity seen in these latter hybridomas was associated with the antigen specificity of the hybridoma cells. Cells expressing these 'unique' TCR junctional sequences were stimulated to produce cytokines both by hsp and by minor-histocompatibility-specific irradiated peritoneal cells. Cells expressing TCR with a common gamma-chain junctional sequence were stimulated to cytokine production by MHC-matched but minor-histocompatibility mismatched (as well as matched) peritoneal cells, but not by hsp. We suggest that p.v. immunization results in stimulation of both antigen-specific and non-specific regulatory gammadeltaTCR+ cells, which can be distinguished by gamma-chain TCR sequence diversity.