Segmental Tracheal Replacement in Mongrel Dogs

Objective—To evaluate the use of alcohol- and detergent-preserved tracheal allografts in dogs. Material and Methods—Experimental segmental tracheal replacement was performed in 18 adult mongrel dogs. Three different techniques were tried in three groups of dogs. In the first group, a four-ring cervical tracheal segment was dissected out and implanted in the trachea of another dog. In the second group, the procedure was performed using a tracheal allograft that had been preserved in 70% ethyl alcohol for 20 days. In the third group, tracheal grafts were previously impregnated in 10% povidone iodine for 72 h before being implanted. Allografts were harvested 60 days after transplantation and assessed both histologically and in terms of the percentage patency. Dogs that died within 60 days were also included in the analysis. Results—The best results were found in the group in which the tracheal allograft had been preserved in ethyl alcohol and this was explained by the reduced antigenicity of the graft in this group. Conclusions—The use of alcohol-preserved allografts is a practical method of tracheal transplantation, and the alcohol-preservation technique markedly reduces the immunogenicity of the grafts.     

Effect of fibrin matrix and vascular endothelial growth factor on reepithelialization of orthotopic murine tracheal transplants

To determine whether the administration of vascular endothelial growth factor (VEGF) alone and in combination with fibrin matrix accelerates murine tracheal allograft reepithelialization, we randomly assigned 40 age-matched mice to 5 experimental groups. BALB/c tracheal grafts were transplanted orthotopically into allogeneic C57BL/6 recipients. The recipients were immunosuppressed with cyclosporine (25 mg/kg per day) and treated with a single topical dose of fibrin matrix, a single topical dose of VEGF, or a single topical dose of a combination of VEGF and fibrin matrix. Thirty-five and 50 days after transplantation, a mixed lymphocyte reaction was performed to assess adequate immunosuppression and the grafts were assessed for rejection, rate and quality of allograft reepithelialization, and cartilage viability. The administration of a combination of fibrin matrix and VEGF to tracheal allografts demonstrated an increased rate of reepithelialization and increased density (37% +/- 2.9%) of morphologically normal ciliated pseudostratified epithelium when compared with an immunosuppressed control group (29.3% +/- 9.1%) 35 days after transplantation. The treated allografts demonstrated no significant change in cartilage viability or rejection. We conclude that the administration of fibrin matrix and VEGF to immunosuppressed tracheal allografts improves the rate and density of tracheal allograft reepithelialization. Carrier-bound growth factors may represent a novel approach to accelerating tracheal allograft reepithelialization and decreasing the need for prolonged immunosuppression following tracheal transplantation.     

Orthotopic tracheal allografts undergo reepithelialization with recipient-derived epithelium

BACKGROUND: While the rejection of heterotopic tracheal allografts is characterized by complete airway obliteration, the rejection of orthotopic allografts leads to airway edema and cellular infiltrate of the lamina propria, but is not associated with obliteration. We hypothesized that orthotopic tracheal allografts undergo reepithelialization with recipient-derived mucosa and that this process prevents airway obliteration. METHODS: Thirty mice were randomly assigned to 6 experimental groups. BALB/c donor tracheal segments were transplanted orthotopically or heterotopically into syngeneic BALB/c or major histocompatability mismatched allogeneic C57BL/6 recipients. Recipients of allogeneic grafts were divided into a nonimmunosuppression group and an immunosuppression group (cyclosporine, 7 mg/kg per day). Twenty-one days after transplantation, histological assessment, immunohistochemistry for CD4 and CD8 lymphocyte infiltration and major histocompatibility-specific immunohistochemistry were performed on the grafts to assess rejection and donor or recipient origin of tissue. RESULTS: Untreated heterotopic allografts underwent complete airway obliteration by day 21. This response was prevented with cyclosporine immunosuppression. Untreated orthotopic allografts, however, demonstrated edema and lymphocytic infiltrate of the lamina propria resulting in clinical stridor without airway obliteration. Immunosuppressed orthotopic allografts did not develop edema or infiltrate of the lamina propria and consequently stridor did not occur. Immunohistochemical analysis demonstrated migration of recipient-derived mucosa into the donor allograft segment in both the untreated and treated orthotopic groups. CONCLUSIONS: Airway obliteration characteristic of rejecting heterotopic tracheal allografts does not occur in the orthotopic allografts. Migration of recipient mucosa into the donor allograft appears to prevent airway obliteration in the orthotopic allografts. These findings suggest that the orthotopic tracheal transplantation model more accurately represents the biological behavior of clinical tracheal allografts than the traditional heterotopic model.     

Reepithelialization of orthotopic tracheal allografts prevents rejection after withdrawal of immunosuppression

Prior work has demonstrated that immunosuppressed orthotopic tracheal allografts undergo progressive reepithelialization over a 48-day period with recipient-derived tracheal epithelium. We hypothesized that reepithelialization of tracheal allografts would prevent rejection after withdrawal of immunosuppression. BALB/c murine tracheal grafts were transplanted orthotopically into either syngeneic or allogeneic C57/BL6 recipients. The recipients were either not immunosuppressed, immunosuppressed with cyclosporine A (10 mg/kg per day) continuously, or immunosuppressed for 48 days and then withdrawn from immunosuppression. The grafts were assessed for acute and chronic rejection 10 days and 50 days after immunosuppression withdrawal. The immunosuppressed allograft recipients maintained a ciliated epithelium acutely and chronically after immunosuppression withdrawal. Ten days after immunosuppression withdrawal, there was a mild cellular infiltrate, which resolved 50 days after withdrawal. Electron microscopy, lymphocyte subpopulation assays, and lamina propria analysis demonstrated that immunosuppression withdrawal did not result in tracheal allograft rejection. In vitro and in vivo assessments did not demonstrate evidence of systemic or local immune tolerance. We conclude that reepithelialization of orthotopic tracheal allografts with recipient-derived mucosa prevents rejection of allograft segments. Tracheal transplantation may require only transient immunosuppression, which can be withdrawn after tracheal reepithelialization.     

同种异体软骨修复甲状软骨缺损的实验研究

OBJECTIVE: To study the effect of laryngeal cartilage defect repair with differently preserved allogeneic cartilage grafts. METHODS: 16 New Zealand white rabbits were used and divided into two groups. A 6 mm x 3 mm x 1 mm whole thickness cartilage defect was made in each side of the thyroid cartilage of each rabbit. In group one, the tissue-cultured cartilage grafts, preserved in RPMI-1640 medium for 30 days, were implanted in the left defects and the 4% formaldehyde preserved cartilage grafts for 30 days were implanted in the right defects. Fresh autogenous and allogeneic grafts were seprately transplanted into the right and left thyroid cartilage defects of the other group. Thyroid cartilages were taken out at 7, 30, 180 and 360 days after implantation. Samples were observed by macroscopy and prepared for hematoxylin and eosin (H&E) staining and immunohistochemical examination. RESULTS: No marked changes in form and volume were found in the fresh allografts and RPMI-1640 cultured cartilage grafts. The same as the autogenous cartilages, the defects of thyroid cartilage were successfully repaired by the fresh allografts and RPMI-1640 cultured cartilages. Whereas 4% formaldehyde preserved cartilage grafts were completely absorbed and replaced by cicatricial tissues in the thyroid cartilage defects. Histological observation showed that severe inflammatory cellular infiltration in the formaldehyde preserved cartilages at 7 and 30 days. The cartilage matrixes were resorpted and the chondrocytes showed degenerative change. Finally they were replaced by fibrous connective tissue at 360 days. In the RPMI-1640 cultured and fresh allogeneic cartilages only a little inflammatory cellular infiltration was observed and the cartilage matrixes were almost normal from 7 to 360 days. CONCLUSION: It is clinically feasible to use allogeneic grafts stored in RPMI-1640 medium or fresh allogeneic cartilage grafts for repairing laryngeal cartilage defects.     

Tracheal reconstruction using alcohol-stored homologous cartilage and autologous cartilage in the rabbit model

OBJECTIVE: Reconstruction of laryngotracheal stenosis continues to pose a significant challenge. Cartilage grafts have been in use for almost a century, but despite good clinical results, many questions concerning the survival and growth of implanted cartilage persist. To reduce donor site morbidity, the use of homologous cartilage has been investigated. This study compared alcohol-stored homologous auricular cartilage with autologous auricular cartilage for anterior graft laryngotracheal reconstruction in a rabbit model. METHODS: Autologous and alcohol preserved homologous auricular cartilage was transplanted to the resected anterior tracheal wall of the twenty New Zealand rabbits. Rabbits were sacrificed 6 weeks after surgery and histologic analysis was performed on the implanted cartilage grafts. RESULTS: The autografts were significantly more likely than the homografts to demonstrate viable cells (95% vs. 30%, P<0.05) and less likely to exhibit significant resorption, fibrosis or necrosis (P<0.05). Resorption and necrosis were most common in areas of trauma to the graft. Complete epithelialization occurred in all of the autografts but in only 65% of the homografts (P<0.05). New cartilage formation and integration of the implanted grafts was poor with both types of grafts. CONCLUSION: Autologous cartilage appears to have better survival than alcohol preserved homologous cartilage when used for anterior graft laryngotracheal reconstruction in a rabbit model.     

A comparison of class II antigenicity of human tracheal allografts stored in cialit and in merthiolate

This report deals with some of the immunological aspects of the transplantation and preservation of human tracheal grafts. The immunological behavior of the transplanted graft depends largely on the interaction of the preservatives with the tissue proteins. Using monoclonal antibodies and the immunoperoxidase staining technique we have investigated the effect of Merthiolate, Cialit, formaldehyde/Merthiolate, and formaldehyde/Cialit preservation techniques on monomorphic determinants of class II transplantation antigens in human tracheal allografts. Unpreserved grafts were found to express class II antigens. These antigens were totally destroyed after 7 days in formaldehyde and 42 days in Cialit and Merthiolate. Preservation in Cialit and Merthiolate showed a gradual disintegration of the histological structures. In contrast, buffered formaldehyde did not appear to alter the histological structure of the tracheal graft. Irrespective of the mode of preservation, the cartilaginous tissue appeared to persist virtually unaffected. No essential differences were observed between the immunological staining of tracheal grafts preserved in Cialit and Merthiolate.     

Microvascular transplantation of tracheal allografts model in the canine

The inability to reconstruct extensive and often life-threatening tracheal defects is a clinical dilemma. The objective of this study was to achieve microvascular revascularization and transplantation of long-segment circumferential tracheal allografts in a canine model. Fifteen mongrel dogs were randomly assigned to 5 treatment groups. Twelve dogs underwent an excision of an 8-cm tracheal segment followed by transplantation and microvascular revascularization of an 8-cm cervical trachea allograft. Group 1 (n = 4) was treated with 10 mg/kg per day of cyclosporin A (CsA) and 7.5 mg/kg per day of mycophenolate mofetil (MM). Group 2 (n = 4) was treated with 5 mg/kg per day of CsA and 7.5 mg/kg per day of MM. Group 3 (n = 4) was treated with 2.5 mg/kg per day of CsA and 7.5 mg/kg per day of MM. Group 4 (n = 2) underwent an autograft tracheal transplant and received postoperative 2.5 mg/kg perday of CsA and 7.5 mg/kg per day of MM. Group 5 (n = 1) did not undergo surgery, but received postoperative 2.5 mg/kg per day of CsA and 7.5 mg/kg per day of MM. The animals were maintained for a duration of 30 days, during which time the graft was assessed by routine endoscopic examination and tracheal biopsies. Ex vivo, tracheal autografts were examined grossly for graft healing and microscopically for histologic architecture. The mean survival times were 13.25 days (group 1), 16 days (group 2), and 20 days (group 3). There was 1 early allograft failure secondary to microvascular thrombosis, and there were 4 delayed failures secondary to postoperative wound infections. Five dogs were euthanized before the end of the 30-day observation period because of failure to thrive or hypocalcemic tetany. None of the dogs in the study demonstrated endoscopic or histologic evidence of rejection before euthanasia. Postmortem examination of the surviving dogs demonstrated normal histologic architecture without evidence of rejection. For the first time, we have achieved allotransplantation of long tracheal segments based on the cranial thyroid artery and internal jugular vein. Minimal systemic immunosuppression appears to be associated with a higher survival rate and a lower complication rate.     

Effect of fibroblasts on epithelial regeneration on the surface of a bioengineered trachea

OBJECTIVES: Our group applied a tracheal prosthesis, which was composed of polypropylene as the frame and collagenous sponge as the scaffold, to the first human case and had successful results. The objective of this study was to find a way to acquire more rapid re-epithelialization with fibroblasts on this tracheal prosthesis. METHODS: Tracheal epithelial cells, which were isolated from the trachea of rats, were suspended in a collagenous gel. The collagenous gel with fibroblasts was layered on a collagenous sponge. The grafts of this "bioengineered trachea" were implanted into tracheal defects of rats, and the regenerated epithelium on the grafts was histologically examined. RESULTS: Seven days after implantation, stratified squamous epithelium covered almost all of the surface of the gel, and some of the implanted fibroblasts in the gel were lined up just below the epithelium. Fourteen days after implantation, columnar and cuboidal ciliated epithelium covered almost all of the surface of the defects, and the implanted fibroblasts had disappeared. The numbers of regenerated epithelial cells at 14 days after implantation were larger than those of control models without fibroblasts, with statistical significance. CONCLUSIONS: The results suggested that the grafts of bioengineered trachea composed of collagenous sponge and collagenous gel with tracheal fibroblasts accelerated epithelial differentiation and proliferation in vivo.     

大鼠喉同种异体移植术后组织学观察

为探讨大鼠同种异体喉移植免疫排斥反应发生的时间和发展过程，共实施大鼠喉移植术３１只。其中对照组（ｎ＝１３）：供、受体均为封闭群ＳＤ大鼠，属同系喉移植术。实验组（ｎ＝１８）：供体为封闭群ＳＤ大鼠，受体为Ｗｉｓｔａｒ大鼠，属同种异体移植术。免疫排斥反应开始于术后第３天，表现为受体颈部皮肤肿胀，淋巴结肿大，７天后颈部皮肤硬肿显著，移植物组织水肿，逐渐被纤维结缔组织包裹。相应的组织学变化特点是：术后第３天变化与对照组基本相同，５天后实验组粘膜上皮逐渐出现鳞状上皮化生，固有层和粘膜下层腺体发生萎缩并消失，横纹肌变性坏死，上述各层组织出现进行性淋巴细胞、单核细胞和多形核白细胞浸润，血管纤维素样变性，管壁增厚，管内血栓形成，１４天后喉移植物的正常组织结构被纤维结缔组织和肉芽组织取代，最终出现完全性变性坏死。由此判断了同种异体喉移植免疫排斥反应发生的时间、顺序和程度，为免疫抑制剂的应用及功效评价提供了客观依据。     

大鼠喉同种异种移植术后组织学观察

为探讨大鼠同种异体喉移植免疫排斥反应发生的时间和发展过程，其实施大鼠喉移植术３１只，其中对照组（ｎ＝１３）；供，受体均为封闭群ＳＤ大鼠，属同系喉移植术。实验组（ｎ＝１８）；供体为封闭群ＳＤ大鼠，受体为Ｗｉｓｔａｒ大鼠，属同种异体移植术。免疫排斥反应开始于术后第３天，表现为受体颈部皮肤肿胀，淋巴结肿大，７天后颈部皮肤硬肿显著，移植物组织水肿，逐渐被纤维结缔组织包裹。相应的组织学变化特点是：术后第３天     

Long-term results of homograft reconstruction of the trachea in childhood

BACKGROUND: The treatment of long-segment tracheal stenosis in children is a biological and operative problem. The introduction of preserved allografts established new possibilities for functional tracheal reconstruction. The development of tracheal dimensions in the course of growing is often discussed. PATIENTS AND METHODS: Since 1983 preserved allografts were used in 20 children with acquired tracheal stenosis. The children ranged in age from 1 to 13 years (average: 7.2 years) when the operation was performed. The children were examined postoperatively at adequate intervals. Radiologic measurements of the tracheal dimensions were performed in some of the patients. RESULTS: Today the treatment of all of these children is complete. Some of them are now adults. None of the children demonstrated breathing problems at the time of the end of treatment or after a variable following-up period ranging from 18 months to 14 years. There was no endoscopic or radiographic evidence of constriction in the growing tracheas. Radiographic measurement of the reconstructed tracheas showed an age-adequate growth in length and a small growth in diameter. CONCLUSION: Functional tracheal reconstruction for long-segment tracheal stenosis can be achieved by implantation of preserved allografts even in the early childhood.     

Freeze-Dried microarterial replacement allografts in rabbits

Microvascular techniques offer important alternatives for reconstructive head and neck surgery. To test the viability of freeze-dried allografts, a pilot experimental study was performed using the rabbit model. Freeze-dried preserved arterial allografts were implanted into femoral artery defects in eight subjects. After 6 weeks, all grafts were harvested and prepared for histologicol and electron microscopic analysis. Immediate patency was 100%. One subject was excluded on the third postoperative day. Of the seven remaining grafts, three (43%) were patent at 6 weeks. These results are comparable to previous data obtained using freeze-dried arterial allografts in the some animal model. Although further investigation is required, this pilot study suggests possible future application of cryopreserved vascular micrografts.     

Tracheal reconstruction with preserved tracheal homograft--new aspects

BACKGROUND: The treatment of long-segment tracheal stenosis is a biological and surgical problem. The introduction of preserved allografts established new possibilities for functional tracheal reconstruction. PATIENTS AND METHODS: Since 1979 preserved allografts were used in 112 patients (including 20 children) with tracheal stenosis. Increasing knowledge in preservation, surgical treatment and pathohistology were put into practice. RESULTS: Implantation of the preserved allografts into the infrahyoid muscles proved to be advantageous. Preservation with the tutoplast method prevented the risk of viral infection, and led to faster and trouble-free post-operative healing. Pathohistological studies let to improve surgical techniques by increasing the knowledge of the nature of tracheal stenosis. CONCLUSION: Functional tracheal reconstruction for long-segment tracheal stenosis can be achieved by implantation of preserved allografts.     

The use of muscle autograft or nerve allograft denatured by microwave for repair of gaps in rat facial nerve]

OBJECTIVE: Attempt to enhance recovery of rat facial nerve through different grafts. METHODS: Rats facial nerve mandible branch gap was repaired using different grafts, either muscle autograft or sural nerve allograft denatured by microwave. Axonal regeneration was studied in 10th week after insertion of the denatured muscle autografts or sural nerve allografts and compared with results found in autologous sural nerve grafts used as controls. Axonal regeneration, Schwann cell behavior and efficacy of nerve and muscle were quantified using CB-HRP retrograde trace, HE staining, Flamming staining and electromyography. RESULTS: Denatured nerve allografts and muscle autografts supported the higher rates and volumes of axonal regeneration. Nerve allografts had the higher degree of myelin sheath developing. CONCLUSION: Nerve autograft and muscle autograft denatured by microwave are convenient, source sufficient, higher efficient grafts for repairing facial nerve gap and have potential clinical use.     

带孔钛环外支撑游离皮片重建气管缺损的动物实验

目的 探讨带孔钛环外支撑游离皮片重建颈段气管缺损的可行性.方法 12只成年杂种犬随机均分为两组.实验组切除颈段气管前壁、侧壁约2/3周径,长约25 mm(4个气管环),制作人工气管缺损模型,取腹部全厚游离皮片修复气管缺损,皮片外部由带孔钛环悬吊支撑.对照组手术模型及缺损修复与实验组相同,但未放置钛环.术后1个月及6个月行X线及纤维支气管镜检查,观察钛环固定情况及管腔情况.术后6个月处死动物,病理检查移植物组织学变化.结果 实验组动物1只术后第5天出现伤口感染裂开,皮片坏死,钛环脱落排出,予以处死;其余5只存活,无呼吸困难;X线摄片示气管腔通畅,钛环固定良好,无移位、变形;纤维支气管镜检查见管腔通畅,管壁光滑,未见狭窄、挛缩及坏死,其中1只在远心端吻合口有少量肉芽,不影响呼吸.存活动物术后6个月处死后病理检查示移植皮片表面大部分覆盖假复层柱状上皮,但上皮覆盖不连续;未见到毛囊,毛发等皮肤附件结构.3只对照组动物术后24 h内死于窒息,尸检发现管腔塌陷皮片水肿;另外3只术后出现不同程度的呼吸困难,最长存活16 d,术后14 d纤维支气管镜检查示管腔塌陷狭窄.结论 带孔钛环可重建气管支架,游离皮片可作为气管黏膜替代物,是气管重建的简便方法之一.     

Transplantation of fresh allografts (homografts) of crushed and uncrushed cartilage and bone: A 1-year analysis in rabbits

Fresh allografts (homografts) of cartilage and bone, crushed and uncrushed, were transplanted in 53 rabbits. Each material was implanted into the auricle and concomitantly into the subdermis of the face. Postoperative assessment was every 1 to 3 days; sacrifice was at 6 weeks, 6 months, and 1 year for microscopic evaluation. Uncrushed cartilage allografts remained viable, and no significant resorption occurred. Crushed cartilage was significantly resorbed by 6 weeks but changed little after that. Resorption of uncrushed bone was moderate and appeared to be ongoing. Total resorption by 1 year occurred in the absence of contact with perichondrium or periosteum. Crushed bone, like crushed cartilage, was largely resorbed. These data document the fact that uncrushed cartilage is superior to crushed cartilage, crushed bone, or uncrushed bone for fresh allograft transplantation in the rabbit and that uncrushed cartilage is probably superior to all other fresh allografts for use in the clinical setting.     

Use of the peritracheal fold in the dog tracheal transplantation model.

OBJECTIVE: To investigate the technical aspects of the canine model of human tracheal transplantation for potential application to reconstruction of extremely long tracheal defects (> 10 cm). DESIGN: In phase 1, long tracheal segments were skeletonized and pedicled with the thyroid glands, cranial thyroid arteries and veins, and internal jugular vein branches. The segments were elevated completely, attached to the vascular pedicle only, and replaced with primary tracheal anastomoses. In phase 2, long segments were elevated along with a diffuse soft tissue "blanket" that envelops the trachea and thyroid glands. Because this study was designed to primarily address, in situ, tracheal perfusion territories of a cranially located vascular pedicle, microvascular anastomoses were not conducted. SUBJECTS: Two small-bodied beagles (10-15 kg) and 5 large-bodied mixed-breed dogs (20-30 kg) were humanely killed 2 to 41 days after surgery, and anatomic and histological analyses were conducted. RESULTS: Unlike that of humans, the thyroid gland complex of dogs is not intimately associated with the trachea but is conjoined with a peritracheal soft tissue "fold." Within this fold, blood is transmitted to the trachea via a diffuse, segmental vascular plexus. In phase 1, pronounced tracheal necrosis occurred within 2 to 5 days. In phase 2, extremely long tracheal segments (10-12 cm), based only on a cranially located pedicle, were still viable at 2 to 6 weeks. CONCLUSIONS: Preservation of the "peritracheal fold" in the dog model of tracheal transplantation is critical to the onset and maintenance of vascular perfusion in a long tracheal segment. Furthermore, the use of large-bodied dogs is necessary to provide for a usable venous efflux component.     

Pretreatment with portal venous ultraviolet B-irradiated donor alloantigen promotes donor-specific tolerance to rat nerve allografts

OBJECTIVE: To determine if a single intraportal inoculation of ultraviolet B-irradiated (UVB) donor splenocytes can prevent nerve allograft rejection and confer donor-specific immunotolerance to rat nerve allograft segments. METHODS: Age-matched, class I and class II major histocompatibility complex (MHC) mismatched Buffalo (RT1b) rats were transplanted with a syngeneic nerve isograft, a Lewis (RT1l) nerve allograft, or a Brown-Norway (RT1n) rat nerve allograft segment. Control Buffalo rats in group I received a 3.0-cm Lewis (RT11) sciatic-posterior tibial interposition nerve allograft without pretreatment; group II Buffalo rats received a syngeneic Buffalo nerve isograft without pretreatment.Group III Buffalo recipients were inoculated with 2.5 x 107 UVB-irradiated Lewis donor splenocyte cells by portal venous administration 7 days before transplantation with a 3.0-cm sciatic-posterior tibial nerve allograft from a Lewis (RT11) or a third party Brown-Norway rat (RT1n) donor (group IV). Nerve graft regeneration was assessed with walking track analysis, nerve conduction studies, retrograde neural tracing, nerve graft histology, and morphometry. Recipient immune tolerance was assessed through in vitro immunological assessment. RESULTS: Pretreatment with UVB-irradiated donor splenocytes 7 days before transplantation prevented nerve allograft rejection. Pretreated animals receiving a nerve allograft recovered limb function, and demonstrated morphological, histological, and electrophysiologic parameters of nerve regeneration similar to that measured in rats receiving a nerve isograft. In vitro immunological assessment by mixed lymphocyte culture (MLC), cytotoxic T lymphocyte (CTL) assay, limiting dilution analysis (LDA) of helper (pTH) and cytotoxic (pCTL) precursor frequencies, and IL-2 production demonstrated a marked donor-specific suppression in allografted animals pretreated with intraportal UVB-irradiated donor splenocytes. These assessments correlated with indefinite acceptance of donor nerve allografts. CONCLUSIONS: A single pretreatment with a single intraportal dose of UVB-modified donor antigen specifically induces tolerance to peripheral nerve allografts in rats.     

微波变性自体骨骼肌和异体神经修复面神经缺损的实验研究

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