Corneal Transplant Rejection Research Articles

Infectious keratitis in patients undergoing Boston Type 1 keratoprosthesis (Boston KPro) procedure: case series

Description of two cases of infectious keratitis in patients after Boston Type 1 keratoprosthesis (Boston KPro) implantation. The first case refers to a patient that had the device indicated due to limbal deficiency secondary to severe dry eye who presented a fungal infection by Aerobasidium pullulans that was successfully treated with amphotericin B eye drops. The second case reports a patient with Boston KPro implantation due to previous corneal transplant rejection showing bacterial keratitis in the fourth postoperative month. The etiologic agent was identified as Streptococcus sp and topical treatment with vancomycin was effective. The importance of postoperative surveillance in Boston KPro eyes is discussed.

Controversies in Ocular Inflammation and Immunology Laser Flare Photometry

Laser flare photometry (LFP) is a method used to detect flare in the anterior chamber (AC). Until now several laser flare photometers have been developed and are in use. LFP is not yet used in all major uveitis centres and, in order to understand this reluctance and know whether use of LFP is justified and should be recommended, an expert meeting was deemed necessary leading to this publication.Besides others results included the following:There is variation between users with regard to how many readings are necessary varying from 3 to 10. It appears appropriate to use at least 6–10 readings. LFP is most useful in patients with anterior uveitis. In patients with posterior and intermediate uveitis, at least 15 photons in the anterior chamber is considered the necessary threshold to be reliable to monitor evolution of inflammation. Factors influencing the measurement of LFP are cataract, corneal opacity, pupil size, intraocular lens and shallow anterior chamber but this is mostly irrelevant in pathological situation. LFP can be used to adjust the management of patients with uveitis, but not necessarily influence treatment. Exceptions may be patients with JIA and Behcet’s Disease. LFP results should always be interpreted in conjunction with the usually clinical observations. There is some evidence that worsening of the flare on two consecutive visits is predictive of a relapse, especially in patients with Behcet’s disease. LFP maybe also useful for predicting rejection of corneal transplant when the cornea is not thickened.

Management of Corneal Graft Rejection – A Case Series Report and Review of the Literature

PURPOSE: To report long-term results in a case series of patients treated with systemic immune suppression for prevention of penetrating keratoplasty (PKP) graft rejection. DESIGN: Retrospective noncomparative chart review. PARTICIPANTS: Three patients presented with PKP graft failure. METHODS: Patients received oral prednisone, azathioprine and cyclosporine to prevent rejection of repeat corneal transplant. Patients received repeat PKP and graft outcome was reported. MAIN OUTCOME MEASURES: Visual acuity and graft survival were recorded. RESULTS: Mean age was 55 years, two male and one female. Mean follow-up period was 37 months (range 24-46). All three patients completed the treatment protocol with minimal adverse effects. All grafts remained clear over observational period. CONCLUSION: Our study suggests that systemic immune suppression with 2 or more agents may be helpful to prevent corneal graft rejection in high-risk patients.

Expression of regulatory T cells and related cytokines in mice allogenic corneal transplantation rejection

To study the changes of CD4(+)CD25(+) and CD8(+)CD103(+) regulatory T cells and their relevant cytokines in corneal allograft transplantation in mice. BABL/c (H-2(d)) mice received corneal allografts from C3H/He (H-2(k)) mice were served as the experimental group. BABL/c (H-2(d)) mice received corneal from BABL/c (H-2(d)) mice were used as the control group. Corneal graft survival time was recorded pre-, 3rd day, 7th day, 4th week, 8th week post-operatively. Infiltration of inflammatory cells and corneal neovascularization were evaluated by histopathologic examination. The percentage of CD4(+)CD25(+) and CD8(+)CD103(+) T cell in peripheral blood and spleen was determined by flow cytometry. The expression of interleukin-10 (IL-10), IL-4, gamma-interferon (IFN-gamma) and IL-1beta in serum and aqueous humor was measured by enzyme-linked immunospecific assay (ELISA). The graft rejection in experimental group occurred at 7 days to 4 weeks after the operation, averaged (14.79 +/- 1.02) days. The grafts in the control group remained clear within 8 weeks observation and the survival time is much longer than that of the allografts (chi(2) = 46.934, P = 0.000). Flow cytometry showed that the percentage of CD4(+)CD25(+) T cell in peripheral blood in the control group after surgery was (3.36 +/- 0.29)%, (4.09 +/- 0.44)%, (5.44 +/- 0.35)%, (5.73 +/- 0.53)% at day 3, day 7, 4th week, and 8th week, respectively, which was significantly higher than that in the experimental group [(2.50 +/- 0.39)%, (3.24 +/- 0.25)%, (4.20 +/- 0.45)%, (4.18 +/- 0.14)%; t = 3.828, 2.898, 3.780, 4.892; P < 0.05]. On the other hand, CD8(+)CD103(+) T cell in peripheral blood in the experimental group after surgery was (2.20 +/- 0.33)%, (2.79 +/- 0.57)%, (4.55 +/- 1.03)%, (4.31 +/- 0.07)% at different periods, which was much higher than that in the control group (t = 7.133, 4.876, 5.196, 19.960; P < 0.05). The changes of CD4(+)CD25(+) and CD8(+)CD103(+) T cells in the spleen was earlier than those in peripheral blood. ELISA showed the expression of IL-10 and IL-4 in the serum in experimental group after surgery was much lower than that in the control group (t = 3.203, 3.141, 3.012, 2.869 and 2.340, 6.681, 8.839, 8.574; P = 0.011, 0.012, 0.013, 0.019 and 0.053, 0.000, 0.000, 0.000). The serum levels of IFN-gamma and IL-1beta in experimental group were higher than that in the control group (t = 3.508, 3.265, 4.402, 5.539 and 3.630, 5.796, 1.728, 0.660; P = 0.006, 0.011, 0.002, 0.000 and 0.005, 0.000, 0.115, 0.524). Furthermore, the cytokine levels in the aqueous humor behaved similarly with those in the serum. The down-regulation of CD4(+)CD25(+) Treg, IL-10 and IL-4 and the up-regulation of CD8(+)CD103(+) Treg, IFN-gamma and IL-1beta in mice allograft corneal rejection may play an important role in allograft rejection.

Effects of Topical and Subconjunctival Bevacizumab in High-Risk Corneal Transplant Survival

To investigate whether corneal graft survival could be improved by topical or subconjunctival bevacizumab in a murine model of vascularized high-risk corneal transplantation. Before corneal transplantation, intrastromal sutures were placed for 2 weeks in the corneas of BALB/c mice, inducing intense angiogenesis. Allogeneic corneal transplantation was performed using C57BL/6 donor mice. Topical bevacizumab (2.5%) was delivered 3 times a day for 3 weeks in one treatment group, and 0.02 mL (0.5 mg) bevacizumab was injected subconjunctivally at days 0, 4, 8, and 15 after transplantation in the other treatment group. The control group received no treatment. Grafts were examined twice a week for 8 weeks by slit-lamp microscopy and were photographed once a week by slit-lamp digital camera and scored for opacity. For assessment of corneal neovascularization (NV), a quantitative method was used to measure three primary metrics including neovascular area, vessel caliber, and neovessel invasion area. Both topical and subconjunctival bevacizumab treatment reduced neovascular area and vessel caliber; however, the regression of corneal NV was more profound when treated subconjunctivally. The mean percentage reduction of neovascular area was 55% (P < 0.05) by week 8 in the subconjunctival treatment group and 33% (P = 0.15) in the topical group. Only subconjunctival bevacizumab treatment resulted in significant regression of neovessel invasion area (P < 0.05). All corneal transplants in both the control and the topical groups were rejected by 4 weeks after transplantation. However, in the subconjunctival treatment group, 33% of corneal grafts survived (P < 0.01). Subconjunctival bevacizumab may offer an adjunctive measure to conventional therapies in preventing graft rejection in high-risk corneal transplantation.

Use of ultrasonic pachymetry for measurement of changes in corneal thickness in mouse corneal transplant rejection

Background/aimsDiagnosis of rejection in the mouse model of corneal transplantation is based on subjective judgement of loss of graft transparency. The aims of this study were to (1) evaluate a...

Oligopeptide-mediated gene transfer into mouse corneal endothelial cells: expression, design optimization, uptake mechanism and nuclear localization

Gene transfer to the corneal endothelium has potential in preventing corneal transplant rejection. In this study, we transfected mouse corneal endothelial cells (MCEC) with a class of novel arginine-rich oligopeptides. The peptides featured a tri-block design and mediated reporter gene expression in MCEC more efficiently than the commercial polyethylenimine standard. The functionality of each block was demonstrated to critically influence the performance of the peptide. Results from confocal imaging and flow cytometry then showed that energy-dependent endocytosis was the dominant form of uptake and multiple pathways were involved. Additionally, uptake was strongly dependent on interactions with cell-surface heparan sulphate. Fluorescence resonance energy transfer studies revealed that the peptide/DNA entered cells as an associated complex and some will have dissociated by 8.5 h. Large-scale accumulation of uncondensed DNA within the nucleus can also be observed by 26 h. Finally, as a proof of biological relevance, we transfected MCEC with plasmids encoding for the functional indoleamine 2,3-dioxygenase (IDO) enzyme. We then demonstrated that the expressed IDO could catalyse the degradation of l-tryptophan, which in turn suppressed the growth of CD4+ T-cells in a proliferation assay.

Rejet d’allogreffe de cornée après Descemet stripping automated endothelial keratoplasty (DSAEK) : à propos de trois cas

Descemet stripping automated endothelial keratoplasty (DSAEK) is an exciting alternative to standard full-thickness penetrating keratoplasty (PK) for the treatment of patients suffering from endothelial failure of the cornea. Corneal transplant rejection is the leading cause of endothelial failure after PK. While DSAEK may reduce the risk of corneal allograft rejection, endothelial rejection can still occur. We report three cases of endothelial rejection after DSAEK. Subacute endothelial rejection occurred in all three cases after the topical steroid treatment regimen had been stopped. A lower rejection rate in comparison with PK cannot be assumed and comparative studies are necessary. Extended topical steroid may be used. Subacute endothelial graft rejection implies that the patient needs to be fully informed of the functional signs and the need to seek medical advice immediately.

Differential Roles of Direct and Indirect Allorecognition Pathways in the Rejection of Skin and Corneal Transplants

It is generally accepted that all transplants are not rejected in the same fashion. However, the extrinsic and intrinsic factors that control the recognition and rejection of a particular allograft by the host are not well characterized. We compared the mechanisms underlying the response with donor antigens by T cells activated after transplantation of fully allogeneic skin and corneal grafts in mice. In corneal-transplanted mice, the CD4+ T-cell response was exclusively mediated by T cells recognizing minor antigens in an indirect fashion and producing low levels of interleukin-2. In contrast, skin grafts elicited both direct and indirect CD4+ T-cell responses primarily directed to major histocompatibility complex antigens and characterized by high interleukin-2 levels. Although CD8+ T-cells producing gamma interferon were activated directly in both skin- and corneal-grafted mice, only CD8+ T cells from skin-transplanted mice mounted a cytotoxic response. Next, we investigated whether failure of corneal transplants to induce a CD4+ direct alloresponse is due to their poor immunogenicity or due to the site of placement (eye). We observed that corneas transplanted under the skin and splenocytes transplanted in the eye were both capable of inducing direct CD4+ T-cell alloreactivity. This shows that failure of orthotopic corneal allotransplants to elicit a CD4+ T-cell direct alloresponse is associated with the combination of two factors, their low immunogenicity and the immune-privileged properties of the eye.

Corneal Lymphangiogenesis: Implications in Immunity

The lymphatic system is a network of vessels throughout the body that serves to return lymphatic fluid to the systemic blood circulation and serves as the immune system's highway in the afferent limb of the immune response. This paper reviews the basics of structure, function and development of the lymphatic system. The emphasis is on understanding the role of lymphatics in the cornea as related to angiogenesis and the clinical setting of corneal transplant rejection.The lymphatic system has two main functions: to drain excess extracellular fluid from capillary beds to return to the systemic blood circulation and to capture antigen for presentation to the immune system in the lymphoid compartment (e.g. nodes) connected in parallel to the lymphatic system. The normal cornea is devoid of lymphatic vessels and blood vessels, thus allowing for its unique immune privileged status. Abnormal blood vessel growth into the cornea has been studied for many years, but the study of lymphatic vessels has been hampered until the recent discovery of lymphatic-specific markers. Subsequent studies of vascularized corneas support the presence of lymphatic vessels in the cornea. The growth of new lymphatic (lymphangiogenesis) and blood (hemangiogenesis) vessels in the cornea is closely related to the abrogation of the immune privileged status of the cornea. This review summarizes our current understanding of the parallel development of hemangiogenesis and lymphangiogenesis as related to the mechanisms of immune rejection of corneal transplants.

Increased Rac2 mRNA expression in peripheral blood during human corneal graft rejection

Allograft rejection is the main cause of graft failure in human corneal transplantation, for which underlying pathomechanism is not yet clear. We compared gene expression in the peripheral blood of patients who after undergoing corneal transplantation experienced graft rejection with those patients who accepted grafts. Sixty-six patients who underwent corneal transplantation were studied including 18 patients who suffered subsequent graft rejection. cDNA array technology was used to survey and quantify transcript expression. A semiquantitative reverse transcriptase-PCR (RT-PCR) was used to confirm the gene expression pattern measured by a cDNA array of selected genes. Among 265 genes present on the array, eight genes were found to be differentially expressed. Four genes (Rac 2, RhoA, paxillin, and CD18) were further analysed by semiquantitative RT-PCR, and significant differences in mRNA expression levels in the rejection group were confirmed. Our study demonstrated that the expression of Rac2 mRNA was upregulated in the peripheral blood of patients experiencing corneal transplantation rejection compared to those patients who had no rejection episodes. In addition, three genes, RhoA, paxillin, and CD18, showed decreased expression in rejecting patients. cDNA array technology provides a potentially useful approach to identify novel genes that might participate in pathogenic pathways during corneal graft rejection.

Rejeição de transplante de córnea

Corneal transplant rejection is an immunological cellular process that attacks the donor cornea and may cause its failure. It is the most common cause of corneal transplant failure.The most common factors for rejection are corneal neovascularization, previous graft failure, anterior synechiae, large or descentered graft, intraocular inflammation and previous anterior segment surgeries. It commonly presents with hyperemia, ocular pain, corneal edema, and anterior chamber inflammation. Corneal graft rejection can be classified as epithelial rejection, subepithelial rejection, stromal rejection, endothelial rejection, [...]

Case–control study of subconjunctival triamcinolone acetonide injection vs intravenous methylprednisolone pulse in the treatment of endothelial corneal allograft rejection

To assess the safety and effectiveness of treating corneal endothelial rejection with a subconjunctival injection of 20 mg triamcinolone acetonide in combination with topical application of 1% prednisolone acetate, as compared to treatment with an intravenous pulse of 500 mg methylprednisolone in combination with topical application of 1% prednisolone acetate. A case-controlled study including a literature review was performed. Patients who presented with an initial episode of corneal endothelial rejection were treated with subconjunctival injection of 20 mg triamcinolone in combination with topically applied 1% prednisolone and were retrospectively matched for age and diagnosis to patients who received a single intravenous injection of 500 mg methylprednisolone in combination with topical 1% prednisolone. Patients were analysed regarding reversion of the rejection episode, intraocular pressure, and visual acuity after 1 year. Overall, the triamcinolone group had a better outcome regarding reversion of corneal transplant rejection (P=0.025), with 15 of 16 patients in the triamcinolone group having clear grafts, compared to only 10 of 16 patients in the methylprednisolone group. Intraocular pressure (IOP) was increased in both groups at day 30 (P=0.002), although there was no statistically significant difference in IOP between the groups (P=0.433). Visual acuity improved in both groups after 1 year (P=0.049), although slightly more improvement was observed in the triamcinolone group (P=0.002). The results observed in this case-controlled study suggest that the use of subconjunctival triamcinolone acetonide may benefit patients with corneal transplant rejection.

Age-related changes in murine limbal lymphatic vessels and corneal lymphangiogenesis

Important risk factors for graft rejection after corneal transplantation are pathologic corneal lymphangiogenesis and young recipient age. Purpose of this study was to investigate whether there are age-related differences in normal murine limbal and pathologic corneal lymphatic vessels, which could partly explain the unequal outcome of corneal transplantation in young versus old recipients. Furthermore, we investigated whether these observed differences correlate with changes in allograft survival in the murine model of corneal transplantation. Corneal whole mounts from untreated young (aged 6–8 weeks), untreated old (aged 9–15 months) and young and old mice after suture-induced, inflammatory corneal neovascularization were prepared and stained with LYVE-1 as a lymphendothelial marker. Angles of corneal parts with and without a main circumferential limbal lymphatic vessel were measured and then related to the total 360° of corneal circumference. Centrally directed vascular extensions from the main limbal lymphatic vessel (“sprouts”) of previously untreated old mice were counted. Concerning the outgrowth of pathologic lymphatic vessels after inflammatory corneal neovascularization, the area covered with pathologic lymphatic vessels was detected by an algorithm on digitized whole mounts using cell^F ® software. Low-risk allogeneic (C57Bl/6 to BALB/c) corneal transplantations were performed with one recipient group being young, the other group being old mice. In young, untreated mice, 70.5% of the total corneal circumference was covered by a main circumferential limbal lymphatic vessel versus 60.8% in old, untreated mice. Comparing the number of centripedal vascular extensions from the main limbal lymphatic vessel (“sprouts”), untreated old mice had significantly less extensions than young, untreated mice ( p < 0.001). After an inflammatory stimulus, old mice had significantly less pathologic corneal lymphatic vessels than young mice (42% less, p < 0.001). Comparing the survival proportions after corneal transplantation, old recipient mice showed a significantly better graft survival 6 weeks after transplantation (65% versus 33%, p < 0.05). Thus, limbal lymphatic vascular sprouts and inflammation-induced pathologic corneal lymphangiogenesis decrease with age. The lower lymphangiogenic potency of older mice may explain the better outcome of corneal transplantations in old recipients, supporting the concept that lymphangiogenesis is an important risk-factor for corneal transplant rejection.

Corneal transplant rejection

The purpose of this article is to review the clinical findings of different types of corneal graft rejection and examine the different options of therapy, including well-established and new treatment modalities. A PubMed literature review search was performed, targeting recent articles on the subject of corneal graft rejection and therapies over the past 40 years. The conclusions of the review were that there are many types of corneal graft rejection, including epithelial, stromal, endothelial, or any combination thereof; 30% of patients will experience rejection episodes within the first year. Different therapies exist for the treatment of corneal transplant rejection. Corticosteroids can be administered by many routes and are the established standard for the treatment of corneal graft rejection. Cytotoxic agents, such as azathioprine can also be used for treatment, however, side effects and toxicity may limit its use. Cyclosporine is an increasingly used therapy for the treatment and prevention of corneal graft rejection, especially in patients at high risk of rejection, and can be produced to be taken orally or made into different strength topical formulations. Tacrolimus and rapamycin are the newest pharmaceuticals used to treat corneal graft rejection.

Medication in corneal transplant rejection

目的 探讨治疗角膜移植术后排斥反应的有效药物.方法 我院近2年全身及局部应用抗排斥反应药物的方法治疗角膜移植术后的排斥反应成功者34例(48眼),进行回顾性研究分析,总结药物治疗的经验.结果 48眼成功病例均为局部应用皮质类固醇者.其中21眼配合全身应用皮质类固醇及免疫抑制剂;27眼局部滴用环胞霉素A滴眼液;4眼应用FKS06滴眼液.全部病例角膜植片恢复透明或半透明.46眼视力恢复至排斥反应发生前水平.结论 在诸多的抗排斥反应药物中,皮质类固醇仍然是首选及非常有效的药物.尤以局部应用为抗排斥反应必不可少的治疗措施。

CTLA4-FasL protein for the prevention of immune rejection in mouse corneal transplantation

To investigate the therapeutic effect of double-functioned CTLA4-FasL protein for the prevention of immune rejection in murine corneal allografts. It was a experimental study. C57BL/6 mice (n = 45) were as donors and BALB/c mice (n = 90) as recipients. BALB/c mice accepted penetrating keratoplasty were randomly divided into 3 groups including no therapy (A), CsA DDS implanted in anterior chamber (B), 10 microg/mL CTLA4-FasL (C). Survival time of corneal allografts was observed and routine assays were performed including immunohistochemistry, reverse-transcription polymerase chain reaction (RT-PCR), TdT-mediated dUTP nick end labeling (TUNEL). Survival time of corneal transplants was (14.3 +/- 1.3) days, (58.0 +/- 2.8) days, (106.3 +/- 17.5) days respectively. There was significant difference between groups in statistics analysis (P = 0.000). Inflammatory cells, predominant for CD4 + T cells, showed an increasing tendency for rejected corneal allografts in A group, peaked on postoperative 7 d and then decreased in C group compared with invisible in B group. CD80 or CD86 was detected on postoperative 3 d or 7 d respectively in excised cornea and iris of both A and B group, while either showed weakening expression in C group. On postoperative 14 d, IL-10, TNF-alpha, IFN-gamma mRNA were only detected in rejected cornea allograft of A group other than clear allografts of B or C group. Compared with no apoptosis in the other groups, abundant apoptosis cells were visible in cornea and iris of C group on postoperative 7 d. CTLA4-FasL is able to prolong survival time of corneal allografts by dual action mechanism to exert immunosuppressive effects, both blockade of CD28-CD80/86 pathway and induction of apoptosis of T cell.

Corneal Transplant Rejection Rate and Severity After Endothelial Keratoplasty

To examine the corneal transplant rejection rate and the rate of graft failure subsequent to rejection in the first 2 years after endothelial keratoplasty (EK) and to compare this to background data for similar cases of penetrating keratoplasty (PK). Anonymized data from consecutive cases of EK [deep lamellar (DLEK) or Descemet stripping (DSEK)] for Fuchs corneal endothelial dystrophy or pseudophakic bullous keratopathy operated on before August 2004 were collected in 4 participating centers. The number and timing of rejection episodes and cases of subsequent graft failure were recorded, together with the time to cessation of topical steroid medication. Two-year postoperative findings were compared with background data for similar patients undergoing PK recorded in the Swedish Corneal Transplant Registry. Rejection episodes were less frequent after EK than PK (P = 0.035). Fifteen (7.5%) of 199 EK cases had a rejection episode in the first 2 years after surgery versus 92 (13%) of 708 PK cases. Graft failure after rejection in EK may have been less frequent than in PK (P = 0.063), with only 1 (6.7%) case of rejection after EK versus 26 (28.3%) cases of rejection after PK proceeding to graft failure. A strong trend toward continued use of low-dose topical steroid medication was observed in the EK group. Eighty percent of EK patients were still taking topical steroid medication 2 years after surgery, whereas topical steroid medication had been ceased within a year of surgery in almost all PK patients in the comparator group. Corneal transplant rejection is less frequent and may be less severe after EK than after PK. It is not yet clear whether these apparent differences are simply a product of relatively prolonged postoperative topical steroid cover in EK patients.

Graft failure IV. Immunologic mechanisms of corneal transplant rejection

Corneal transplantation is the oldest and the most common form of solid tissue transplantation in humans. Immunologic graft rejection is one of the main causes of short and long-term graft failure. Rejection involves donor tissue recognition and destruction by allo-specific immune cells of the recipient. This review outlines (1) the immunobiology of transplantation, with reference to ocular immune privilege, (2) factors that confer "high-risk" status to a graft and (3) the pathophysiologic mechanisms of corneal transplant rejection.

Lymphangiogenesis concurrent with haemangiogenesis in the human cornea

Corneal transplant rejection can occur with and without neovascularization; therefore, it is necessary to elucidate what other factors allow for rejection. It has been suggested that the lymphatic system may play a role in graft failure, but it has also been held that the cornea is devoid of lymphatics. Use of a new monoclonal antibody against a lymphatic endothelial marker, D2-40, has been used to detect lymphatics in other tissues. The purpose of this study was to use this new tool to determine if the human cornea can undergo lymphangiogenesis. Twelve corneal buttons submitted for routine pathology were subjected to immunohistochemical staining with a monoclonal antibody against D2-40 to detect the presence/absence of lymphatics by light microscopy. By the criteria defined, lymphatic vessels were identified in seven out of 12 corneal buttons. In these cases, there was also evidence of neovascularization. Lymphatic positive buttons included four cases where there were histological markers of inflammation. There were no identifiable lymphatics in the remaining five cases and no sign of vascularization. Corneal lymphatics were identified in association with corneal neovascularization, via the use of a monoclonal antibody against D2-40. In non-vascularized corneas, lymphatics were absent.