Patterns of immune rejection of mouse neocortex transplanted into neonatal rat brain, and effects of host immunosuppression

We studied the histological and immunological characteristics of graft rejection in the rodent central nervous system (CNS) using embryonic mouse neocortex transplanted into the CNS of neonatal rats. Grafts from animals aged 8-145 days (n = 210) were examined using standard histological techniques for demonstrating cell morphology and fiber projections. Immunohistochemical techniques were used to identify graft projections into the host CNS. The incidence of graft rejection was 18% for animals between 18 and 30 days of age, but increased abruptly to 73% for animals older than 30 days. No graft rejection was seen in animals younger than 18 days. In a smaller group of xenograft recipient rats sacrificed at specific time points before and after one month of age, detailed immunohistochemical studies were performed to correlate the histological appearance of the graft with the level of major histocompatibility complex (MHC) class I and II immunoreactivity, and microglial, astrocytic and lymphocytic staining within the graft and host brain. Evidence of mild rejection as manifested by the appearance of scattered lymphocytes within the graft coincided with the development of Class I and II immunoreactivity within the graft and at the graft-host interface, which was demonstrated in some animals as early as 24 days. At 29 days of age, rejecting grafts showed diffuse MHC expression within the graft and at the graft-host interface; in contrast, unrejected grafts failed to show MHC immunoreactivity. Thirty-four day-old grafts often showed severe rejection with perivascular lymphocytic cuffing within the graft and in host parenchyma remote from the graft associated with increased MHC immunoreactivity within the host brain. In grafts older than 34 days there was frequently a violent rejection reaction with disruption of the cytoarchitecture of the graft and surrounding host tissues, and widespread MHC antigen expression. Immunosuppression with cyclosporin A was effective in avoiding rejection. The high incidence of rejection with neocortical xenografts is in striking contrast to the much lower incidence seen with retinal xenografts. This suggests that there are immunological features unique to neocortex which incite host recognition and rejection.     

BN rats do not reject F344 brain allografts even after systemic sensitization

Embryonic brain tissue allografts under many circumstances survive transplantation into the brain. It is generally believed that such grafts will not survive if the host animal is systemically sensitized, by skin grafting or other means, to major histocompatibility complex (MHC) antigens of the donor animal. We have found that F344 brain grafts survive in BN hosts even when the host is systemically sensitized to F344 tissue. Embryonic cerebral neocortex from F344 donors was transplanted into BN host rats (n = 95). Subsequently, the host rats were systemically sensitized with donor skin (n = 25), brain tissue (n = 41), or spleen cells (n = 6) and compared with a control group of rats consisting of allografts with no sensitization or sham procedures (n = 23). Rejection of the transplants in BN rat hosts was not provoked by any of the sensitization methods tested. Minor immunological responses that did not result in rejection were, however, present in many host animals. We did not observe infiltration of W3/13+ T cells and OX8+ cytotoxic lymphocytes in any of the groups. Nevertheless, substantial infiltrations of OX6+ antigen-presenting cells and W3/25+ helper T cells were present. There was also an extensive enhancement of MHC class I immunoreactivity in parts of the grafted tissue developing within the third ventricle, but not for the same type of graft in the lateral ventricle. This increase of MHC class I expression was not accompanied by infiltration of cytotoxic T cells. Our findings thus suggest that neural graft rejection depends on general genetic susceptibility to immune reactions, particularly experimental allergic encephalomyelitis and not only on disparity between donor and host antigens encoded by the MHC. Moreover, enhancement of MHC class I and class II expression within transplanted tissue does not predict graft rejection.     

Leukocyte infiltration and glial reactions in xenografts of mouse brain tissue undergoing rejection in the adult rat brain. A light and electron microscopical immunocytochemical study

Neural mouse xenografts undergoing rejection in the adult recipient rat brain were characterized with regard to infiltrating host leukocytes and reactions of graft and host astro- and microglial cells. Rejection occurred within 35 days with infiltration of the grafts by in particular macrophages and T-cells as well as blood-brain barrier (BBB) leakage for IgG. In the surrounding host brain microglial cells showed increased histochemical staining for nucleoside diphosphatase (NDPase) and increased immunocytochemical expression of complement receptor type 3 (CR3), while astroglial cells displayed an increased immunoreactivity for glial fibrillary acidic protein (GFAP). Light microscopic findings of rat major histocompatibility complex (MHC) antigen class I on microglial cells, endothelial cells and leukocytes were confirmed at the ultrastructural level and extended to include a few astrocytes. Rat and mouse MHC antigen class II was only detected on leukocytes and activated microglia. We suggest that host macrophages and activated host and xenograft microglial cells act in situ as immunostimulatory cells on T-helper cells, and that increased levels of donor MHC antigen class I may further enhance the killer activity exerted by host T-cytotoxic cells.     

Allogeneic grafts of fetal dopamine neurons: immunological reactions following active and adoptive immunizations

To define the importance of adoptive sensitization and duration of graft residence on transplant alloimmunization, behavioral and histochemical parameters were examined in unilaterally 6-OHDA-lesioned F344 rat hosts which received fetal ventral mesencephalic (VM) grafts from Wistar-Furth (WF) donors. In all animals which showed increased rotations after alloimmunization, increased numbers of T cell receptor (TcR) positive, CD8⁺ lymphocytes were detected in the grafts. In addition, an increased density of class I MHC antigens was seen in the graft and in the adjacent host brain. Lesser numbers of CD4⁺, CD11b⁺, and MHCII⁺ positive elements were also seen. Perivascular cuffing was often found in actively immunized animals. An increase in TcR⁺ and MHC class I⁺ elements was also seen in animals only adoptively immunized. The tyrosine hydroxylase positive graft area was also markedly reduced in actively immunized animals and the extent of reduction correlated with the number of cells used for immunization. These studies indicate that established allografts can evade rejection as long as host lymphocytes are not activated against graft alloantigens. In addition, increasing graft residence time in the host and adoptive immunization render the graft more susceptible to subsequent rejection.     

Immunological reactions to neural grafts in the central nervous system

Immunological rejection is a lasting, although highly variable, threat to allo- and xenogeneic neural tissue grafted to the CNS of rodents, monkeys and man. One major determinant for rejection of intracerebral CNS grafts appears to be induction of major histocompatibility complex (MHC) antigens on the donor CNS cells. We have previously examined the cellular immune response against neural mouse xenografts undergoing rejection in the adult rat brain. In this study we focus on the astro- and microglial reactions within and around the graft, and the potential of individual host rat and donor mouse brain cells to express MHC antigens. Previous light microscopical observations of expression of rat MHC antigen class I by endothelial cells, microglial cells, and invading leukocytes were extended to the ultrastructural level and found to include a few astrocytes. Rat and mouse MHC antigen class II was only detected on leukocytes and activated microglial cells. The findings imply that within grafts of brain or spinal cord tissue donor astrocytes, microglial cells and endothelial cells can be induced to act as target cells for class I specific host T cytotoxic cells, while only (graft and host) microglial cells can be induced to express MHC antigen class II and present antigen to sensitized (and possibly also resting) host T helper cells.     

Immunological reactions induced by intracerebral transplantation: evidence that host microglia but not astroglia are the antigen-presenting cells

The immunological reactions to embryonic cerebellar xenografts (n = 16) and allografts (n = 8) in host rat brain were studied after 2, 4, and 6 weeks of survival and compared to a control group consisting of 10 rats with isografts. Indirect immunofluorescence was performed on fresh frozen brain sections using antibodies against antigen presenting cells (Ia/Ox-6+ cells) and T helper (W3/25+) cells. Massive infiltrations of both cell types were found within xenografts. Ia antigen was present in the walls of small vessels near the transplant as well as in the ventricles on supra- and subependymal cells. In host tissue surrounding the grafts, Ox-6+ immunoreactivity was also observed in a population of cells ranging from an irregular rod-like shape with short branching processes to more rounded cell bodies with retracted processes. The appearance of these cells was characteristic of microglia. These cells were GFAP-negative. These cellular reactions were associated with rejection of the grafts. In contrast, the allografts survived, but nevertheless cells expressing Ox-6+ and to a lesser extent W3/25+ immunoreactivity were found along the injection needle tract and in damaged host tissue surrounding the grafts. No Ox-6+ perivascular infiltrations were seen. Some staining was also found within the allografts, mainly associated with damaged tissue. Ox-6+ ramified cells were also observed. Both Ox-6+ and W3/25+ immunoreactivity decreased with the time of survival. Host and donor GFAP-positive astrocytes did not express Ox-6+ molecules, and therefore probably were not involved in presenting antigen to effector cells. The control isografts also survived very well, but nevertheless Ox-6+ and less widespread W3/25+ cells were present in surrounding injured host tissue. Ox-6+ perivascular infiltration was not found in the host brain of animals with isografts. Ox-6+ and W3/25+ immunoreactivities were present primarily in graft areas that appeared damaged, often closely associated with injured host tissue. These results indicate that the process of implantation of grafts and associated brain injury induces enhanced Ia/Ox-6+ immunoreactivity, primarily on microglia in brain parenchyma surrounding grafts, and suggest that host microglia may substantially contribute to the initiation of immune reactions against intracerebral grafts. Despite this predisposition to an immunological response, only in the case of xenografts did these reactions, with the addition of Ox-6+ perivascular cuffing and cell infiltrations within the grafts, lead ultimately to graft rejection.     

The blood-brain barrier protects foreign antigens in the brain from immune attack

To examine the role of the blood-brain barrier (BBB) in maintaining immune privilege in the brain, the BBB in the region of stably integrated mouse neural grafts implanted in neonatal rat brains was transiently disrupted by intracarotid infusion of hypertonic mannitol. This led to graft rejection and to prominent expression of major histocompatibility complex (MHC) antigens on cells adjacent to the graft. Grafts in control animals receiving an intracarotid infusion of isotonic saline showed only rare MHC expression and no increased incidence of rejection. Opening the barrier in the absence of a graft caused neither MHC expression nor cellular infiltration within the brain, suggesting that the effects of the hypertonic infusion were not produced by an indirect injury-mediated effect on the host brain. We conclude that the integrity of the blood-brain barrier is an important factor in the relative immune privilege of nonsyngeneic neural grafts.     

Integrity of the blood-brain barrier in retinal xenografts is correlated with the immunological status of the host

The purpose of this study was to determine the immunological correlates of blood-brain barrier breakdown in retinal xenografts in rats by utilizing skin grafting to initiate a timed immune response to the transplanted neural tissue. Embryonic day 13-14 CD-1 mouse retinae were grafted into the brainstem parenchyma of neonatal Sprague-Dawley rats. In one group of animals a 100 mm2 CD-1 skin graft was placed on the flank 21 days after the initial neural transplant in order to provoke an immune response to the neural graft. Control animals received no skin graft. Animals were injected with horseradish peroxidase (HRP) in the femoral vein 2-8 days after skin grafting. Brains were processed for Nissl, HRP-tetramethylbenzidine, and anti-M-6, -lymphocyte, -macrophage, and -astrocyte antibodies. Experimental and control animals injected 2-4 days after skin grafting showed no leakage of reaction product in the grafted tissue. A small percentage (one of eight) of 5-day animals showed isolated, patchy leakage, but no evidence of rejection of the neural graft. At 6 days all of the grafts showed evidence of leakage, and 71% of these grafts showed infiltration of lymphocytes. By 7-8 days extensive leakage of HRP and widespread infiltration of lymphocytes and macrophages were clearly evident. The present study demonstrates that blood-brain barrier breakdown is correlated closely with the sequence of immunological rejection of the graft. While these results confirm that a barrier exists in healthy neural transplants, they suggest that immunological factors should be considered in cases in which grafts are not protected by an intact barrier.     

Characterization of the microglial response in murine scrapie

The nature of the glial and inflammatory cell responses to infection in scrapie–affected brains was studied in terminally–affected mice of Ave scrapie models. There were marked astrocytic and microglial responses. Microglia showed increased staining of the surface antigens F4/80, leucocyte–common antigen, type 3 complement receptor, and elevated endocytotic and lysosomal activity. In all models, the astrocytic and microglial responses were largely restricted to anatomical regions of the brain showing vacuolation and/or plaque formation and pathological accumulations of PrP. Expression of MHC Class II was patchy and present on microglia in the neuropil of areas with the most intense microglial activation and on occasional perivascular macrophages. This microglial response may represent a modified form of inflammatory response.     

Behavioral and anatomical correlates of immunologically induced rejection of nigral xenografts

Cell suspensions derived from the ventral mesencephalon of CD-1 mice were unilaterally transplanted into the striatum of neonatal Sprague-Dawley rats that had been bilaterally dopamine depleted. Thirty-eight percent of the grafts survived. Tyrosine-hydroxylase-immunoreactive neurons within the transplant innervated the host striatum with a dense fiber plexus. The grafts appeared to exert some degree of functional control over motor behavior in that these animals made contralateral rotations in response to amphetamine and tail pinch. In order to provide additional evidence that the motor behavior is associated with the transplant itself, the graft was removed. This was achieved by using a mouse skin graft to provoke an immunological response against the transplanted neural tissue. The immunological response resulted in the specific loss of the transplant with little or no damage to the surrounding neural tissue. The amount of rotation observed after tail pinch and amphetamine injection was severely affected by neural graft rejection. The loss of turning was associated most directly with the loss of tyrosine hydroxylase immunoreactivity within the transplant rather than with the massive reduction of tyrosine-hydroxylase-positive fibers in the ipsilateral host striatum. These data suggest that dopamine cells in mouse nigral grafts play an essential role in eliciting rotational behavior in neonatally dopamine depleted rats. They also show the value of skin grafting as a technique for specifically removing neural xenografts.     

Subacute brain-stem encephalitis

A 65 year old man developed progressive signs of pontine and medullary dysfunction with striking bilateral paralysis of lateral gaze, dysarthria, dysphagia, and ataxia. A respiratory death occurred seven months from the onset. Pathological examination revealed focal brain-stem changes of perivascular lymphocytic cuffing, microglial infiltration, glial nodules, and neuronophagia. No underlying malignancy or general disease impairing immunity mechanisms was discovered.     

Fetal neocortical transplants in rats: blood-brain barrier development and partial permeability to IgG in long-surviving grafts

In previous work, allografts of fetal (E13-16) neocortical tissue transplanted into neocortical lesion cavities in newborn (PND 0-1) rats developed an impermeable blood-brain barrier (BBB) as shown by intravascular administration of horseradish peroxidase and by immunohistochemical staining for endogenous IgG. The present study examines the time course for the formation of the graft BBB by staining for endogenous IgG and also looks at transplants with extended survival times of 1-2 years. At two weeks post-transplantation, the grafts of all ten animals of this group showed evidence of IgG immunoreactivity within the graft parenchyma. This was greatest at the pial surface and adjacent to the ventricular surface of the transplant. By three weeks after transplantation, only four of nine grafts showed graft vessel permeability and this was confined to the area under the pia. At four weeks survival, one of nine grafts showed a small rostral patch of IgG reactivity, and a second animal showed very light, diffuse transplant labeling. The remaining seven animals were devoid of transplant IgG reactivity. At 11.5-28 months, three out of seven grafts had reaction product in the graft, indicating BBB permeability to IgG. In two of these older transplants, permeability was confined to the area around larger blood vessels, while one additional animal (28 months) showed dense labeling immediately below the pial surface. As in normal rats, host brain labeling was only found in circumventricular organs. These results show that circulating macromolecules are excluded from most CNS grafts within the first month of transplantation. This process progresses from the center of grafts and requires the longest time to complete in subpial regions possibly associated with healing of the pia. Some older grafts show leakage of protein which may relate to aging of the transplant or to a low-level graft rejection.     

Time-dependent expression of donor- and host-specific major histocompatibility complex class I and II antigens in allogeneic dopamine-rich macro- and micrografts: comparison of two different grafting protocols

Neural transplantation, as a therapeutic approach to Parkinson’s disease, still requires allogeneic graft material and raises questions of immunosuppression and graft rejection. The present study investigated the time course of major histocompatibility complex (MHC) expression and astrocytic response in allogeneic dopaminergic grafts, comparing two different grafting protocols. Adult 6-hydroxydopamine-lesioned Lewis 1.W rats received intrastriatal cell suspension grafts from the ventral mesencephalon of DA rat fetuses, either as single 1-μl macrograft via metal cannula or as four micrografts of 250 nl/deposit via a glass capillary. No immunosuppression was administered. Immunohistochemistry was performed at 1, 3, 6, and 12 weeks after grafting, using antibodies against donor- and host-specific MHC class I and II antigen, glial fibrillary acidic protein (GFAP) and tyrosine hydroxylase (TH). Most animals showed good allograft survival up to 12 weeks after transplantation with no signs of rejection. Reinnervation of the lesioned striatum by TH-positive neurites was observed from 3–6 weeks on. Expression of donor-specific MHC class I was comparably low in both allogeneic grafting groups, while host MHC class I and II reaction as well as astrocytic response tended to be higher in the macrografted animals. Donor MHC class II was not observed at any time point. It is concluded that intraparenchymal allografts of fetal mesencephalic cell suspensions can survive well in the rat Parkinson model without immunosuppression for at least 12 weeks, and that the expression of moderate amounts of donor-specific MHC class I antigen does not suffice to initiate a rejection process. In addition, the microtransplantation approach may reduce the level of trauma and subsequent MHC and GFAP expression and may, thereby, minimize the risk of graft rejection. Received: 14 May 1997 / Revised, accepted: 17 July 1997     

Effects of dexamethasone on microglial activation in vivo: selective downregulation of major histocompatibility complex class II expression in regenerating facial nucleus

Following axotomy of the facial nerve microglial cells in the facial nucleus become activated, proliferate, and newly express class I and class II major histocompatibility complex (MHC) antigens. Dexamethasone treatment, starting 2 days prior to axotomy at 1 mg/kg/day, selectively inhibited axotomy-induced MHC class II expression on microglial and perivascular cells. In contrast, MHC class I expression was not significantly affected, nor was the expression of other microglial activation markers and the light microscopic morphology of activated microglia. A recently suggested inducer of MHC expression in rat nervous tissue, neuronal gamma interferon-like immunoreactive material, was also unaffected, as was glial fibrillary acidic protein immunoreactivity as a marker for concomitant astroglial activation. The differential effects of the drug suggest the presence of distinct regulatory pathways for different aspects of microglial activation. Inhibition of class II expression on activated microglia might be one mechanism how glucocorticoids act in the suppression of neuroinflammatory disease.     

Methylprednisolone prevents rejection of intrastriatal grafts of xenogeneic embryonic neural tissue in adult rats

We studied the effects of high-dose methylprednisolone on the survival of intrastriatal neural xenografts and the host responses against them. Dissociated mesencephalic tissue from inbred mouse (CBA-strain) embryos was transplanted to the intact striatum of adult Sprague-Dawley rats. The rats received either daily injections of methylprednisolone (30 mg/kg), or cyclosporin A (10 mg/kg), or no immunosuppressive treatment. Two or six weeks after transplantation, there was good survival of xenografts in both the methylprednisolone- and cyclosporin A-treated rats. In contrast, the xenografts in untreated control rats were all rejected by six weeks. There was no marked difference in the degree of expression of MHC class I and II antigens and the accumulation of activated astrocytes and microglial cells/macrophages between the three groups. However, both methylprednisolone and cyclosporin A reduced infiltration of T lymphocytes to the transplantation sites. The expression of pro-inflammatory cytokines (interferon-λ, tumour necrosis factor-a, interleukin-6) in and around the grafts was lower in the methylprednisolone- and cyclosporin A-treated groups than in untreated control rats. Although high-dose methylprednisolone caused significant body weight loss, we conclude that this treatment can prevent rejection of intrastriatal grafts of xenogeneic embryonic neural tissue in the adult.     

Survival of intrastriatal xenografts of ventral mesencephalic dopamine neurons from MHC-deficient mice to adult rats

Previous studies of neural xenografts have used immunosuppressive agents to prevent graft rejection. In the present study we have examined the survival of mouse dopamine neurons lacking either MHC class I or MHC class II molecules transplanted into rat brains and the host immune and inflammatory responses against the xenografts. Survival of neural grafts was immunocytochemically determined at 4 days, 2 weeks, and 6 weeks after transplantation by counting tyrosine hydroxylase (TH)-positive cells in the graft areas. In addition, the host immune and inflammatory responses against neural xenografts were evaluated by semiquantitatively rating MHC class I and class II antigen expression, accumulation of macrophages and activated microglia, and infiltration of CD4- and CD8-positive T-lymphocytes. For the negative controls, the mean number of TH-positive cells in rats that received wild-type mouse tissue progressively decreased at various time periods following transplantation. In contrast, intrastriatal grafting of either MHC class I or MHC class II antigen-depleted neural xenografts resulted in a prolonged survival and were comparable to cyclosporin A-treated rats that had received wild-type mouse tissue. These results indicate that genetically modified donor tissue lacking MHC molecules can be used to prevent neural xenograft rejection.     

Progressive expression of immunomolecules on microglial cells in rat dorsal hippocampus following transient forebrain ischemia

Summary We show a differential up-regulation of immunomolecules in the rat dorsal hippocampus accompanying neuronal cell death as a consequence of transient forebrain ischemia (four-vessel occlusion model). Using a panel of monoclonal antibodies (mAbs), we have examined the time course of expression of major histocompatibility complex (MHC) antigens class I (OX-18) and class II (OX-6), leukocyte common antigen (OX-1), CD4 (W3/25) and CD8 (OX-8) antigens, CR3 complement receptor (OX-42), as well as brain macrophage antigen (ED2). The study was performed at time intervals ranging from 1 to 28 days after reperfusion. Throughout all post-ischemic time periods, strongly enhanced immunoreactivity on microglial cells in the CA1 region and dentate hilus and, to a lesser extent, in CA3 was demonstrated with mAb OX-42. MHC class I-positive cells (OX-18) appeared on day 2, whereas cells immunoreactive with OX-1 and W3/25 became evident in the CA1 and hilar regions on post-ischemic day 6. In contrast, MHC class II (Ia) antigen was first detected on indigenous microglia by day 13. In some animals, the OX-8 antibody resulted in the labelling of scattered CD8-positive lymphocytes, but perivascular inflammatory infiltrates were absent. No changes in the expression of ED2 immunoreactivity on perivascular cells could be observed. The results show that following ischemic injury, microglial cells demonstrate a timedependent up-regulation and de novo expression of certain immunomolecules, indicative of their immunocompetence. The findings are compared with those obtained in other models of brain injury.Supported in part by NIH/NINCDS PO 1 NS27511     

Long-term survival of mouse corpus callosum grafts in neonatal rat recipients, and the effect of host sensitization.

Previous studies have suggested that the incidence of spontaneous rejection among immunogenetically mismatched neural transplants in neonatal recipients varies significantly depending on the cellular composition of the graft material. For example, neuron-rich grafts of embryonic mouse retina generally survive for extended periods without showing signs of rejection after implantation into neonatal rats, whereas cortical xenografts, which contain abundant glial and endothelial cells as well as neurons, typically undergo rejection 4-6 weeks after implantation. To determine whether the presence of donor glia is responsible for this high incidence of spontaneous rejection, we examined the fate of a non-neuronal graft material composed predominantly of xenogeneic glial cells (post-natal day 3, PD3, CD-1 mouse corpus callosum) implanted into the mesencephalon of PD1 Sprague-Dawley rats. The distribution and survival of donor astrocytes were assessed using a monoclonal antibody specific for a mouse astrocyte surface antigen, M2. Thirteen of 16 animals sacrificed within 2 months of implantation had detectable transplants. In these animals, M2-positive cells frequently migrated well away from body of the graft, clustering in large numbers in several characteristic regions of the host brain. Unlike cortical grafts of similar age, the vast majority (93%) of callosal transplants showed no histological signs of rejection or major histocompatibility complex antigen expression in and around the transplant-derived cells. As previously noted in the neonatal retinal transplant paradigm, however, well-integrated 1-month-old corpus callosum grafts could be induced to reject by appropriate sensitization of the host immune system, implying that the host was not immunologically tolerant to the foreign neural graft. With longer survival times in unsensitized hosts, a progressively smaller percentage of animals had detectable donor astrocytes (5 of 10 animals at 3 months postimplantation and 4 of 16 animals at 4 months); in those 9 animals with surviving grafts, only small numbers of M2-positive cells were seen within the graft bed and surrounding host brain. However, only 2 of the 26 "long-term" animals showed evidence of graft rejection. These results indicate that mouse astrocytes show characteristic patterns of migration into the host brain when implanted into neonatal rats; however, these xenogeneic cells have a limited duration of survival. The infrequency with which even subtle signs of spontaneous rejection were detected in animals that had received corpus callosum xenografts suggests that an immune-mediated process is unlikely to be responsible for the time-dependent elimination of the donor astrocytes.(ABSTRACT TRUNCATED AT 400 WORDS)     

Astrocytic development in fetal parietal cortex grafted to cerebral and cerebellar cortex of immature rats

Pieces of cortex cerebri anlage were dissected out from 16- to 17-day-old fetuses and transplanted to the cortical and cerebellar regions of 5- to 6-day-old rat pups. Twelve animals with grafts in the cortical region and 5 animals with grafts in the cerebellar region were studied 1.5-4 months later. Cresyl violet stained sections revealed no gross difference in either cell morphology, cell density or cell distribution between grafts in the two locations. A molecular layer-like zone was present on all free surfaces of the grafts, whether facing a ventricle or the meninges. The astrocytic development was studied using immunohistochemistry with antibodies against glial fibrillary acidic protein, (GFA), and the S-100 protein. Both antibodies visualized starshaped astrocytes and perivascular membranes surrounding blood vessels. Semi-quantitative measurements as well as computerized image analysis showed that the total amount of GFA-like immunoreactivity was much higher in both types of grafts than in corresponding host cortex cerebri. No differences in amount of S-100-like immunoreactivity could be demonstrated. As S-100 is thought to be a more general astrocytic marker than GFA, this suggests that the difference in GFA-like immunoreactivity is due mainly to an increased amount of GFA within the individual astrocytes. It is concluded that grafts of fetal cortex cerebri pieces to the CNS of young hosts develop a profound astrocytic reaction characterized by an increased amount of GFA-like immunoreactivity.     

抗ICOS免疫疗法抑制鼠心脏移植的加速性和慢性排斥反应

背景：在DA鼠移植给路易鼠模型中,用AdCTLA-4Ig免疫球蛋白阻断B7-CD28共刺激信号可以诱导心脏同种异体移植的长期免疫耐受。然而这种耐受是不完全的,并最终发生排斥。尤其是在心脏移植后功能良好时将供体皮肤移植给受体可以引发加速性移植心脏的排斥反应。 目的：重新评价抗ICOS抗体疗法与AdCTLA-4Ig疗法相结合在同种异体移植中的作用。验证抗ICOS疗法无论是否应用AdCTLA-4Ig疗法都起到阻断心脏加速性排斥的作用。 方法：在DA(供体)→LEW(受体)鼠之间进行心脏移植手术。心脏移植给予受体鼠一次静脉注射109 pfu AdCTLA-4Ig。生存期> 50 d的受体鼠接受全厚皮片移植到侧胸壁,第50天开始静脉注射抗ICOS抗体(1 mg/kg)或者IgG,隔天注射1次,共2周。完全移植排斥被定义为心脏停止跳动,或者组织学上通过单核细胞浸润和心肌细胞坏死的苏木精-伊红染色证实。 结果与结论：AdCTLA-4Ig处置受体生存大于100 d的心脏切片可见典型的ICOS+单核细胞浸润,并表现出血管病理性改变。AdCTLA-4Ig疗法与抗ICOS抗体结合可介导出对慢性排斥稳定的耐受。抗ICOS疗法明显减少了ICOS阳性炎性细胞浸润,并阻断了皮肤二次移植引发的心脏加速性免疫排斥反应。实验结果表明了ICOS在慢性及急性心脏移植免疫排斥中的重要作用,并揭示出阻断血管化器官同种异体移植慢性排斥的革命性观点。