Surgical technique for vascularized ear transplantation in mice

Traditionally, the mouse nonvascularized skin graft has been widely used in organ transplant research. There are, however, several limitations with this model, the main one being the different immune response of vascularized vs. nonvascularized grafts. We have recently developed a vascularized, orthotopic ear transplant model in mice. This model has several advantages that make it a useful tool to study many aspects of transplantation. The donor operation consists of harvesting the ear with intact arterial and venous pedicles. The arterial pedicle is dissected down to the common carotid artery with ligation of all branches except the auricular artery. The venous pedicle is based on the jugular vein with preservation of the auricular veins draining into the posterior facial vein. In the subsequent recipient operation, the graft is transplanted into an orthotopic position using the common carotid artery for arterial inflow and the jugular vein for venous outflow. We performed 16 such transplants (6 isografts, 5 allografts, and 5 xenografts), with a success rate of 94% (15/16). The donor operation time was 1.5 hours and the recipient operation time was 2.5 hours. The total time for anastamosis was 45 +/- 5 minutes. Serial biopsies were obtained on days 3, 5, and 7, and correlated with gross findings. In summary, this study illustrates that it is technically possible to transplant a mouse ear graft. The main advantage of this model is that it is a vascularized graft that can be visibly observed and easily biopsied, thus allowing for good correlation between gross and histological findings after transplantation. We plan to use this model further to study in detail the rejection patterns in an allograft and xenograft setting.

Organ transplantation in mice: current status and future prospects

With the development of microsurgery and molecular biology in the 1990s, the mouse model for organ transplants has become increasingly popular. In the past 10 years, the number of studies using the mouse model has increased three-fold. All the organ transplants, originally done in the rat model, can now be performed in mice with high success rates. This article reviews the development, advantages, limitations, and unique immunology of the mouse model as well as future prospects.

Technical experiences with a microsurgical model of lymphatic reconstruction after intestinal transplantation in rats

The surgical procedure of intestinal transplantation disrupts the graft's lymphatic drainage. Despite morphological regeneration, the functional impairment of the lymphatic system may contribute to many pathophysiological changes after transplant. We describe the technical details and results of a microsurgical model of lymphatic reconstruction (LR), which immediately reconstitutes lymphatic drainage of the intestinal graft in rats. A total of 42 orthotopic intestinal transplants with LR was performed. The patency of the LR was assessed between postoperative days 2 and 100 using either methylene-blue staining of the lymphatic vessels or mesenteric lymphoradiography. A total patency rate of 88% was achieved. Genetic background, occurrence of rejection, and immunosuppressive treatment with cyclosporine did not affect the patency rate. Technical aspects and potential applications of this model are discussed.

Surgical technique for vascularized thymus transplantation in mice

Traditionally, mouse nonvascularized thymus implants have been used to investigate various aspects of thymus function. However, these grafts are easily damaged by ischemia and fail to reproduce the normal anatomy of the thymus. In addition, the function of these grafts has not been fully examined. We have recently developed a vascularized thymus transplant model in mice. The donor operation consists of isolating the right lobe of the thymus and creating a single vascular pathway. In the recipient surgery, end-to-side anastomoses between donor brachycephalic artery and recipient right common carotid artery, and between donor superior caval vein and recipient right external jugular vein, were performed. We performed 10 consecutive isografts in BALB/c mice with a success rate of 90%. The thymus grafts had a normal histology and function. This study illustrates that it is technically possible to transplant a mouse vascular thymus graft. This model has several advantages that make it a useful tool to study many aspects of thymus function. We plan to use this model further to study the potential for induction of tolerance by thymus grafts.

[Antitumor effect of the extract of birch bark and its influence to the immune function]

OBJECTIVE

To study the antitumor effect of extract of birch bark (EBB) and its influence to the immune function of the tumor-bearing mice.

METHOD

EBB was administered orally and the tumor inhibiting effects were observed in tumor-bearing mice. Experiment of the immune function are to examine thymocytes (spleen) index, reaction of spleen to ConA and activity of NK cell.

RESULTS

EBB showed antitumor effect in vivo to B16, S180 and Lewis lung cancer in mice. EBB can significantly prolong survival period of bearing tumor mice. EBB can enhance thymocytes and spleen index in C57 BL/6 mice. EBB can enhance splenic lymphocytes translate and activit of NK cell (P < 0.05).

CONCLUSION

EBB have antitumor effect and enhance immune function in bearing tumor mice.

The axis of interleukin 12 and gamma interferon regulates acute vascular xenogeneic rejection

Recent advances using transgenic animals or exogenous complement inhibitors have demonstrated prevention of hyperacute rejection of vascularized organs, but not graft loss due to acute vascular rejection. Using various wild-type and cytokine-deficient mice strains, we have examined the mechanisms of acute vascular rejection. C57BL/6 mice deficient in interleukin12 or gamma interferon showed faster acute vascular rejection than did wild-type mice. Furthermore, mice defective in B-cell development showed no acute vascular rejection. These results demonstrate that the axis of interleukin 12 and gamma interferon provides a survival advantage in vascularized xenografts by delaying or preventing acute vascular rejection caused by a B cell-dependent mechanism.

Ectopic deposition of lignin in the pith of stems of two Arabidopsis mutants

The biosynthesis of lignin in vascular plants is regulated both developmentally and environmentally. In the inflorescence stems of Arabidopsis, lignin is mainly deposited in the walls of xylem cells and interfascicular fiber cells during normal plant growth and development. The mechanisms controlling the spatial deposition of lignin remain unknown. By screening ethyl methanesulfonate-mutagenized populations of Arabidopsis, we have isolated two allelic elp1 (ectopic deposition of lignin in pith) mutants with altered lignin deposition patterns. In elp1 stems, lignin was ectopically deposited in the walls of pith parenchyma cells in addition to its normal deposition in the walls of xylem and fiber cells. Lignin appeared to be deposited in patches of parenchyma cells in the pith of both young and mature elp1 stems. The ectopic deposition of lignin in the pith of elp1 stems was accompanied by an increase in the activities of enzymes in the lignin biosynthetic pathway and with the ectopic expression of caffeoyl coenzyme A O-methyltransferase in pith cells. These results indicate that the ELP1 locus is involved in the repression of the lignin biosynthetic pathway in the pith. Isolation of the elp1 mutants provides a novel means with which to study the molecular mechanisms underlying the spatial control of lignification.

Inhibition of transplant vasculopathy in a rat aortic allograft model after infusion of anti-inflammatory viral serpin

BACKGROUND

Transplant vasculopathy remains a difficult therapeutic problem, resulting in the majority of late cardiac graft losses. This chronic vascular disease is thought to be triggered by alloantigen-dependent and alloantigen-independent inflammatory factors. Despite improved 1-year survival, the incidence of transplant vasculopathy has not improved with current immunosuppressive protocols. Highly effective strategies have evolved in the large DNA viruses that shield infecting viruses from host inflammatory responses. Serp-1 is a secreted myxoma virus anti-inflammatory serine proteinase inhibitor. Serp-1 inhibits plasminogen activators in a manner similar to plasminogen activator inhibitor (PAI-1), a vascular protein that plays a pivotal regulatory role in vascular wound healing. In this study, we tested the ability of purified Serp-1 protein to ameliorate posttransplant vasculopathy after rat aortic allograft surgery.

METHODS AND RESULTS

Serp-1 protein or controls were infused into 98 rats immediately after segmental aortic allograft transplantation. After either late (28 days, 64 rats) or early (12 to 48 hours, 24 rats) follow-up, transplanted aortic segments were harvested for morphological and immunohistochemical analysis. Significant reductions in intimal plaque growth (P<0.002) and mononuclear cell invasion (P<0.033) were detected after Serp-1 infusion at nanogram doses. Serp-1 reduced early macrophage (P<0.0016) and nonspecific lymphocyte (P<0.0179) invasion into medial and adventitial layers and inhibited associated depletion of medial smooth muscle cells (P<0.0006).

CONCLUSIONS

Infusion of a viral anti-inflammatory serpin, Serp-1, significantly reduces early inflammatory responses and later luminal occlusion in a rat aortic allograft model.

Induction of metallothionein synthesis with preservation of testicular function in rats following long term renal transplantation

Metallothionein (MT), as an acute phase or stress-response protein and free radical scavenger, is related to inflammation and cellular protection from oxidative damage. In order to evaluate long-term testicular damage and the role of MT following renal transplant, nine allogenic (Fisher 344 --> Lewis) and seven isogenic (Lewis --> Lewis) renal transplants were performed and the recipient rats were followed for 140 days when allografts develop chronic transplant rejection. Testicular weight, light microscopic morphology, and lactate dehydrogenase-X enzyme activity were assessed. Testicular MT was determined by Cd-heme assay, and was localized immunocytochemically using a polyclonal rabbit antibody. No differences in testis weight, morphology, or LDH-X enzyme activity were found between allograft and isograft recipients. Testicular MT level was significantly increased in the testis of allograft recipients. Testicular zinc (Zn) and copper (Cu) levels, but not iron (Fe) level, were significantly higher in testis with allograft kidney than that with isograft kidney. In addition, Cu/Zn ratio was also significantly high in the allograft group. However, the MT level did not show any significant correlation either with Cu and Zn alone or with Cu/Zn and Fe/Zn ratios. These data suggest that allogenic stimuli may induce MT synthesis in the recipient testis. The increased MT level in an allograft may offer a protective action from oxidative damage in the testis.

Prolongation of xenograft survival using monoclonal antibody CD45RB and cyclophosphamide in rat-to-mouse kidney and heart transplant models

BACKGROUND

Intrigued by the finding that a monoclonal antibody (mAb) directed against the B exon of restricted CD45 (CD45RB mAb) induced renal allograft tolerance in the mouse model, we hypothesized that CD45RB mAb may prevent xenograft rejection. We explored the role of CD45RB mAb in preventing xenograft rejection in rat-to-mouse kidney and heart transplant models.

METHODS

Mice with rat kidney and heart xenografts were treated with a short course of mAb, cyclosporine, cyclophosphamide, or mAb + cyclophosphamide combination therapy. Untreated heart and kidney xenografts served as controls.

RESULTS

Untreated controls developed acute vascular and cellular rejection rapidly with a median survival time of only 6 days. Long-term kidney (median survival time = 70 days) and heart xenograft survival (median survival time = 65 days) was achieved using the combination therapy of mAb + cyclophosphamide. One-third of the kidney recipients with combination therapy survived 100 days. Immunohistochemistry and xenospecific-antibody analysis demonstrated that combination therapy remarkably reduced IgG and IgM deposition and also inhibited CD4+, CD8+, and Mac-1+ cell infiltration at early stages. This therapy, however, did not induce tolerance in this model as evoked xenoreactive antibodies and cellular responses may be the cause of late xenograft failure.

CONCLUSION

A short course of CD45RB mAb combined with cyclophosphamide effectively inhibits cellular and humoral immunoresponses and remarkably prolongs xenograft survival in rat-to-mouse heart and kidney transplant models.

Allograft tolerance induced by cyclophosphamide without prior inoculation of donor cells--immune suppression and redirection

OBJECTIVES

To determine the possibility and cellular mechanism of inducing allograft tolerance by multiple injection of a lower dose of cyclophosphamide without prior infusion of donor cells.

METHODS AND RESULTS

Heterotopic heart grafts were performed in MHC mismatched strain combinations (C57/B6 vs. BALB/c). Cyclophosphamide (40 mg/kg) was given intravenously on days 0, 2, 4 and 7 without prior infusion of donor cells. Long-term (> 100 days) allograft survival with normal histology was achieved. The long-term survivors accepted the donor skin grafts, but rejected the third-party skin grafts. Cyclophosphamide treatment initially led to profound lymphocytopenia, inhibition of spontaneous blastogenesis and low levels of lymphocyte proliferation response to both donor and third-party antigens. Ultimately, donor-specific tolerance occurred demonstrated by normal levels of peripheral lymphocytes, spontaneous blastogenesis and lymphocyte proliferation response to third-party antigens, and low levels of lymphocyte proliferation response to donor antigen. A switch of cytokines from IFNgamma dominant to IL-4 dominant, a low level of IgM and a high level of IgG1 were found in tolerant mice.

CONCLUSIONS

Allograft tolerance can be induced by a short course of cyclophosphamide without prior donor cell inoculation. Tolerance induced is characterized initially by non-specific immunosuppression, which progresses to donor-specific hyporesponsiveness associated with the development of a Th2 dominant cytokine response.

Nova-1 regulates neuron-specific alternative splicing and is essential for neuronal viability

We have combined genetic and biochemical approaches to analyze the function of the RNA-binding protein Nova-1, the paraneoplastic opsoclonus-myoclonus ataxia (POMA) antigen. Nova-1 null mice die postnatally from a motor deficit associated with apoptotic death of spinal and brainstem neurons. Nova-1 null mice show specific splicing defects in two inhibitory receptor pre-mRNAs, glycine alpha2 exon 3A (GlyRalpha2 E3A) and GABA(A) exon gamma2L. Nova protein in brain extracts specifically bound to a previously identified GlyRalpha2 intronic (UCAUY)3 Nova target sequence, and Nova-1 acted directly on this element to increase E3A splicing in cotransfection assays. We conclude that Nova-1 binds RNA in a sequence-specific manner to regulate neuronal pre-mRNA alternative splicing; the defect in splicing in Nova-1 null mice provides a model for understanding the motor dysfunction in POMA.

alpha5beta1 integrin expression and luminal edge fibronectin matrix assembly by smooth muscle cells after arterial injury

Fibronectin is secreted from the cell as a soluble protein that must then polymerize to regulate cell function. To elucidate the process of fibronectin matrix assembly in vascular disease, we immunostained sections of balloon-injured rat carotid artery for the fibronectin-binding alpha5beta1 integrin. Whereas alpha5beta1 integrin was not evident in the normal carotid artery, its expression was induced after a vascular injury. By 14 days, the alpha5beta1 integrin was localized exclusively to the less differentiated smooth muscle cells (SMCs) at the luminal surface of the neointima. Platelet-derived growth factor-BB, dominant in neointimal formation, selectively increased the expression of the alpha5beta1 integrin by human SMCs in culture. To track the assembly of fibronectin fibers, fluorescence-labeled soluble fibronectin protomers were added to cultured SMCs and to fresh segments of normal and balloon-injured rat carotid arteries. Fibronectin fiber formation in cultured SMCs could be detected within 10 minutes, and was blocked by an RGD peptide, an anti-beta1 integrin antibody, and an anti-alpha5beta1 integrin antibody, but not by an anti-beta3 integrin antibody. En face confocal microscopy of arterial segments revealed that soluble fibronectin had polymerized on the alpha5beta1 integrin-expressing SMCs of the luminal surface of the injured arterial neointima, but not on the alpha5beta1 integrin-negative neointimal SMCs below this or on the endothelial cells of uninjured arteries. Furthermore, in situ fibronectin assembly by the neointimal SMCs was inhibited by an RGD peptide and by an anti-beta1 integrin antibody. These studies indicate that a subpopulation of SMCs in the repairing artery wall orchestrates integrin-mediated fibronectin assembly.

Reconstruction of the intestinal lymphatic drainage after small bowel transplantation

BACKGROUND

The surgical procedure of small bowel transplantation normally results in complete disruption of the graft's lymphatic drainage. The present study was undertaken to determine the impact of lymphatic reconstruction (LR) on the outcome of intestinal grafting, using a microsurgical model that immediately restores lymphatic drainage.

MATERIALS

Brown Norway (RT1n) intestinal grafts were orthotopically transplanted into Lewis (RT1(1)) rats either with LR (+LR) or without LR (-LR). Recipients were randomly allocated into the following groups: no treatment or cyclosporine (CsA) at a dose of 2, 5, or 10 mg/kg/day subcutaneously from postoperative day (POD) 0 to 6.

RESULTS

There was morphological regeneration of lymphatics in the -LR group between 1-3 weeks as previously reported, whereas normal lymph flow was immediately restored in the +LR group. All untreated and CsA(2 mg)-treated allografts were rapidly rejected in both the +LR and -LR groups. In the groups treated with approximately 5 mg of CsA, five of six -LR animals died of chronic rejection between 38 and 86 days (mean survival time +/- SD: 76.7+/-21 days), while all +LR animals survived until death on POD 100 (P < 0.05). Histological features of mucosal damage found in -LR grafts were absent in the +LR grafts. All of the animals treated with 10 mg of CsA survived indefinitely. Sequential histology revealed mild rejection in -LR and +LR grafts on POD 45, but +LR animals had significantly higher body weight gains (POD 50: -LR: 117+/-12% vs. +LR: 136+/-4%, P < 0.01). LR did not affect donor cell migration and nutritional parameters.

CONCLUSION

LR improves the long-term results of small bowel transplantation resulting in better survival rates, less mucosal damage due to chronic graft rejection, and greater weight gain. We conclude that impairment of lymph flow may contribute to poor outcomes when standard surgical techniques are used for small bowel transplantation.

Complement inhibition with an anti-C5 monoclonal antibody prevents hyperacute rejection in a xenograft heart transplantation model

BACKGROUND

The present study was undertaken to determine whether anti-complement 5 (C5) monoclonal antibodies (mAb) prevent hyperacute rejection (HAR) in a rat-to-presensitized mouse heart transplantation model and whether these mAb, combined with cyclosporine (CsA) and cyclophosphamide (CyP), can achieve long-term graft survival.

METHODS

BALB/c mice were presensitized with 2x10(7) splenocytes from Lewis rats 14 days before grafting. Heart grafts from Lewis rats were heterotopically transplanted into BALB/c mice. Presensitized mice were treated with either anti-C5 mAb or a combination of anti-C5 mAb, CsA, and CyP. Controls included: presensitized mice with no treatment, presensitized mice treated with either CsA + CyP or IgG, and nonpresensitized mice with either no treatment or with CsA + CyP treatment.

RESULTS

Although typical features of HAR were evident in the presensitized grafts, the mAb completely inhibited complement activation and successfully prevented HAR. Despite complement inactivation, the graft was rejected on postoperative day 6 with acute vascular rejection (AVR) also known as delayed xenograft rejection (DXR). Notably, this type of rejection cannot be effectively overcome by CsA and CyP.

CONCLUSIONS

We conclude that (1) anti-C5 mAb prevents HAR, (2) AVR/DXR still occurs when HAR is prevented by complement inactivation, and (3) AVR/DXR cannot be overcome by conventional immunosuppression. These data suggest that anti-C5 mAb may be valuable for preventing HAR in future clinical xenotransplantation and that additional interventions may be required to address AVR/DXR.

IFL1, a gene regulating interfascicular fiber differentiation in Arabidopsis, encodes a homeodomain-leucine zipper protein

Arabidopsis inflorescence stems develop extraxylary fibers at specific sites in interfascicular regions. The spatial specification of interfascicular fiber differentiation is regulated by the INTERFASCICULAR FIBERLESS1 (IFL1) gene because mutation of that gene abolishes the formation of normal interfascicular fibers in Arabidopsis stems. To understand further the role of IFL1 in the specification of fiber differentiation, we cloned the IFL1 gene by using a positional cloning strategy. Sequence analysis showed that the IFL1 gene encodes a transcription factor that has the same features as a family of homeodomain-leucine zipper (HD-ZIP) proteins found only in plants. The predicted IFL1 protein is composed of three distinct domains, including a 60-amino acid HD at the N terminus followed by a 28-amino acid ZIP motif and a 724-amino acid C-terminal region. A nuclear targeting assay showed that IFL1 is able to direct a beta-glucuronidase fusion protein into the nucleus, which is consistent with IFL1's presumed function as a transcription factor. Gene expression analysis demonstrated that the IFL1 gene is expressed in the interfascicular regions in which fibers differentiate, which is consistent with its role in the control of interfascicular fiber differentiation. Furthermore, the IFL1 gene was shown to be expressed in the vascular regions, indicating its possible role in the regulation of vascular tissue formation. This possibility is supported by the observation that differentiation of both xylary fibers and vessel elements is altered in the vascular bundles of ifl1 mutants. Our results provide direct evidence that an HD-ZIP protein plays a role in the spatial control of fiber differentiation.

CD40-deficient dendritic cells producing interleukin-10, but not interleukin-12, induce T-cell hyporesponsiveness in vitro and prevent acute allograft rejection

The induction of an immune response or tolerance is mediated by corresponding subsets of dendritic cells (DC). However, the property of tolerogenic DC is not clear. Recently, we have characterized a population of CD11c+ splenic DC derived from long-term mixed leucocyte culture (LT-MLC), which are able to proliferate upon stimulation and have a strong primary mixed leucocyte reaction (MLR)-stimulating activity in conventional MLR. In this study, we show that, in contrast to the irradiated ones, non-irradiated LT-MLC-derived DC induce polyclonal antigen-specific T-cell hyporesponsiveness when cocultured with allogeneic splenocytes for 3-11 days. The degree of the hyporesponsiveness increased with the length of coculture. Although these DC expressed major histocompatibility complex class II and B7 costimulatory molecules, which are down-regulated during coculture, they expressed very low or undetectable CD40 before and after coculture, respectively. The CD40-deficient DC spontaneously produce interleukin-10 (IL-10), but not IL-12. The skewed balance between IL-10 and IL-12 is associated with their capability to induce T-cell hyporesponsiveness, because a neutralizing antibody to IL-10, exogenous recombinant IL-12 or lipopolysaccharide (LPS) significantly blocked the hyporesponsiveness. Accordingly, infusion of a small number of non-irradiated LT-MLC-derived DC (5x105) significantly prolonged the survival of a vascularized heterotopic murine heart transplant, whereas irradiated DC accelerated graft rejection. These data suggest that CD40-deficient DC producing IL-10, but not IL-12 can induce T-cell hyporesponsiveness in vitro and in vivo.

[Elimination of CD28+ T cell in patients with chronic active hepatitis]

OBJECTIVE

To study the role of toxicyte T cell in active hepatitis.

METHODS

We examined CD28+ T cell in patients with chronic active/remission hepatitis by flow cytometry.

RESULTS

It shows that CD28+, CD8+CD28+ T cell in patients with chronic active hepatitis decreased significantly, compared with normal control or patients with liver cirrhosis and heptoma.

CONCLUSION

It implies that B7-CD28 costimulation pathway contribute to the tissue injury in hepatitis.

A dominant-negative pleiotrophin mutant introduced by homologous recombination leads to germ-cell apoptosis in male mice

Pleiotrophin (PTN) is an 18-kDa heparin-binding secretory growth/differentiation factor for different cell types. Its gene is differentially expressed in both mesenchyme and central nervous system during development and highly expressed in a number of different human tumors. Recently, a PTN mutant was found to act as a dominant-negative effector of PTN signaling. We have now used homologous recombination to introduce the dominant-negative PTN mutant into embryonic stem cells to generate chimeric mice. All highly chimeric male mice with germinal epithelium exclusively derived from embryonic stem cells with the heterologous PTN mutation were sterile. Their testes were uniformly atrophic, and the spermatocytes were strikingly apoptotic at all stages of development. The results support a central role of PTN signaling in normal spermatogenesis and suggest that interruption of PTN signaling may lead to sterility in males.

Domain structure of pleiotrophin required for transformation

The pleiotrophin (PTN) gene (Ptn) is a potent proto-oncogene that is highly expressed in many primary human tumors and constitutively expressed in cell lines derived from these tumors. The product of the Ptn gene is a secreted 136-amino acid heparin binding cytokine with distinct lysine-rich clusters within both the N- and C-terminal domains. To seek domains of PTN functionally important in neoplastic transformation, we constructed a series of mutants and tested their transforming potential by four independent criteria. Our data establish that a domain within PTN residues 41 to 64 and either but not both the N- or C-terminal domains are required for transformation; deletion of both the N and C termini abolishes the transformation potential of PTN. Furthermore, deletion of two internal 5-amino acid residue repeats enhances the transformation potency of PTN 2-fold. Our data indicate that PTN residues 41-64 contain an essential domain for transformation and suggest the hypothesis that this domain requires an additional interaction of the highly basic clusters of the N or C terminus of PTN with a negatively charged "docking" site to enable the transforming domain itself to engage and initiate PTN signaling through its cognate receptor.

Transformation of the collateral vascular bundles into amphivasal vascular bundles in an Arabidopsis mutant

Arabidopsis inflorescence stems develop a vascular pattern similar to that found in most dicots. The arrangement of vascular tissues within the bundle is collateral, and vascular bundles in the stele are arranged in a ring. Although auxin has been shown to be an inducer of vascular differentiation, little is known about the molecular mechanisms controlling vascular pattern formation. By screening ethyl methanesufonate-mutagenized populations of Arabidopsis, we have isolated an avb1 (amphivasal vascular bundle) mutant with a novel vascular pattern. Unlike the collateral vascular bundles seen in the wild-type stems, the vascular bundles in the avb1 stems were similar to amphivasal bundles, i.e. the xylem completely surrounded the phloem. Furthermore, branching vascular bundles in the avb1 stems abnormally penetrated into the pith, which resulted in a disruption in the ring-like arrangement of vascular bundles in the stele. The avb1 mutation did not affect leaf venation pattern and root vascular organization. Auxin polar transport assay indicated that the avb1 mutation did not disrupt the auxin polar transport activity in inflorescence stems. The avb1 mutation also exhibited pleiotropic phenotypes, including curled stems and extra cauline branches. Genetic analysis indicated that the avb1 mutation was monogenic and partially dominant. The avb1 locus was mapped to a region between markers mi69 and ASB2, which is covered by a yeast artificial chromosome clone, CIC9E2, on chromosome 5. Isolation of the avb1 mutant provides a novel means to study the evolutionary mechanisms controlling the arrangement of vascular tissues within the bundle, as well as the mechanisms controlling the arrangement of vascular bundles in the stele.

Cyclosporine inhibits long-term survival in cardiac allografts treated with monoclonal antibody against CD45RB

BACKGROUND

We have previously reported that a monoclonal antibody to CD45RB is a novel immunosuppressive agent; however, the optimal regimen in cardiac allografts remains unknown. The present study was undertaken to determine the optimal protocol of this therapy and its interaction with cyclosporine.

METHODS

A heterotopic heart allograft model was used in C57BL/6 to BALB/c mice. The following studies were conducted: 1) dose response study (low, intermediate, and high doses at 1, 3, and 9 mg/kg/day respectively), 2) short course (2 days) therapy vs. long course (9 days) therapy, 3) pretreatment (starting on day -1) vs no pretreatment, 4) daily therapy vs. alternative day therapy, and 5) monoclonal antibody treatment with and without cyclosporine.

RESULTS

The efficacy of the CD45RB monoclonal antibody was dose and duration dependent (p<0.01). Pretreatment significantly improved the efficacy of this therapy (74.5+/-13.4 days vs. 30.6+/-1.5 days, p<0.01). Daily therapy was superior to alternate day therapy (74.5+/-13.4 days vs. 30.4+/-1.5 days, p<0.03). Interestingly, we found that administration of cyclosporine prior to, at the same time as, or after administration of the CD45RB monoclonal antibody had a detrimental effect on graft survival compared to mAb treated alone (16.6+/-0.4 days, 25+/-2.3 days, and 35.3+/-0.9 days respectively vs. 74.5 days, p<0.01).

CONCLUSIONS

Immunosuppression with CD45RB monoclonal antibody is dose and duration dependent. Pretreatment and daily therapy improves results. Addition of cyclosporine inhibits long-term graft survival achieved by the monoclonal antibody alone.