Coadministration of the new macrolide immunosuppressant RAD and mycophenolate mofetil in experimental corneal transplantation

Mycophenolate mofetil and animal models

Mycophenolate mofetil (MMF), is the morpholinoethyl ester of mycophenolic acid (MPA). Though initially developed as an anti-rejection treatment, MMF is beginning to find application in more common immune-mediated diseases. MMF has been shown to be effective against transplant-associated vascular disease, lupus and other inflammatory diseases via multiple mechanisms in several animal models. MMF treatment blocks the proliferation of T cells and B cells, attenuates the production of autoreactive IgG and IgM, diminishes complement deposition, and reduces the production of multiple proinflammatory cytokines including TNF-α, IFN-γ, IL-2, IL-3, IL-4, IL-5, IL-6 and IL-12. It also increases production of the anti-inflammatory mediator IL-10. In addition, MMF reduces the infiltration of immune cells into sites of inflammation by interfering with the expression of cell-surface molecules critical for this process, including MHC class II, CD40, CD80, CD86, I-A, and ICAM-1. Additional mechanisms involving mannosylation and N-linked glycosylation of cell-surface molecules are only beginning to be investigated. This article will focus on the contribution of animal models of disease as investigational tools in the development of MMF as an immunomodulatory drug. The use of mice, rats, rabbits, monkeys, baboons and interspecific xenografts will be discussed.

[Immunosuppressives to prevent rejection reactions after allogeneic corneal transplantation]

In order to prevent rejection of an allogeneic corneal transplant after perforating (high risk) keratoplasty, active agents from different classes of pharmacological substances are used, as with solid organ transplantation. In addition to glucocorticoids, antiproliferative agents, small molecule inhibitors and antibodies, those belonging to the group of macrolides with their many derivatives represent an interesting class of substances in this context. As a supplement to cyclosporin A (CSA) the most successful macrolide in transplantation medicine, animal experiments are currently being carried out to test newer macrolide derivatives, such as sanglifehrin A (SFA). This overview describes the classes of drugs and modes of action of currently administered standard medications in the clinical routine and new developments are presented.

Topical pimecrolimus does not prolong clear graft survival in a rat keratoplasty model

BACKGROUND

Long-term application of topical steroids following penetrating keratoplasty is disadvantageous due to side effects (steroid response, cataract, surface disorders). In this study we investigated the efficacy of topical pimecrolimus regarding clear graft survival following allogeneic orthotopic keratoplasty in rats.

METHODS

A total of 46 penetrating keratoplasties were performed using Fisher rats (allogeneic groups) and Lewis rats (syngeneic group) as donors and Lewis rats as recipients: group 1 (n = 11), allogeneic control without therapy; group 2 (n = 12), syngeneic control; group 3 (n = 11), mycophenolate mofetil (MMF) 40 mg/kg body weight; group 4 (n = 12), pimecrolimus 1% ointment twice daily. Four animals of each group were sacrificed for immunohistological evaluation on day 14. Therapy was administered for 18 days. The grafts were evaluated once every 3 days regarding opacity, oedema and vascularisation. Graft rejection was defined as total graft opacity.

RESULTS

Mean rejection-free graft survival was 11.4 days in group 1 (allogeneic control), 100 days (total follow-up time) in group 2 (syngeneic control), 24.0 days in group 3 (MMF 40 mg/kg) and 11.6 days in group 4 (topical pimecrolimus). The immunohistological evaluation showed no statistically significant difference in cell infiltration of the grafts comparing groups 1 and 4.

CONCLUSIONS

Topical immunosuppression with pimecrolimus does not prolong graft survival in the allogeneic keratoplasty rat model.

[Systemic immunosuppressives after penetrating keratoplasty]

Immunologic rejection is the main cause of corneal graft failure. If corneal transplantation is performed in a high-risk situation without the use of systemic immunosuppression, corneal graft failure has to be expected in over 50% of patients within the first postoperative year. The clonal expansion of graft-specific lymphocytes occurs in lymphoid tissues. As topical steroids do not reach the secondary lymphoid organs, and even systemic steroids do not interfere sufficiently with the clonal expansion of activated T cells, it is essential to administer systemic immunosuppressives in order to achieve clear graft survival. As corneal transplantation is not a life-saving procedure, the profile of side-effects is a central issue when choosing an immunosuppressive medication.

A new model of corneal transplantation in the miniature pig: efficacy of immunosuppressive treatment

Corneal allograft rejection is frequently studied in small rodent or rabbit models. To study mechanisms of rejection in a model that more closely mimics transplantation in humans, we performed orthotopic corneal transplantation in the miniature pig using a 7-mm diameter donor graft. Four groups of recipients were studied: 1) untreated naive, 2) untreated vascularized (high risk), 3) high-risk grafts treated by topical application of prednisolone, or 4) high-risk grafts treated with a combined systemic immunosuppression regime of oral prednisone, cyclosporine A, and mycophenolate mofetil. Both the clinical features and histological assessment of corneal graft rejection showed close similarities to graft rejection in humans. Interestingly, preliminary results indicated that topical steroid treatment was superior to systemic immunosuppression in significantly promoting graft survival. Thus, corneal transplantation in the pig represents an animal model most closely resembling corneal grafting in humans, and offers possibilities for testing various clinically applicable immunosuppressive treatments.

Corneal Graft Rejection

Penetrating keratoplasty is the most widely practiced type of transplantation in humans. Irreversible immune rejection of the transplanted cornea is the major cause of human allograft failure in the intermediate and late postoperative period. This immunological process causes reversible or irreversible damage to the grafted cornea in several cases despite the use of intensive immunosuppressive therapy. Corneal graft rejection comprises a sequence of complex immune responses that involves the recognition of the foreign histocompatibility antigens of the corneal graft by the host's immune system, leading to the initiation of the immune response cascade. An efferent immune response is mounted by the host immune system against these foreign antigens culminating in rejection and graft decompensation in irreversible cases. A variety of donor- and host-related risk factors contribute to the corneal rejection episode. Epithelial rejection, chronic stromal rejection, hyperacute rejection, and endothelial rejection constitute the several different types of corneal graft rejection that might occur in isolation or in conjunction. Corneal graft failure subsequent to graft rejection remains an important cause of blindness and hence the need for developing new strategies for suppressing graft rejection is colossal. New systemic pharmacological interventions recommended in corneal transplantation need further evaluation and detailed guidelines. Two factors, prevention and management, are of significant importance among all aspects of immunological graft rejection. Preventive aspects begin with the recipient selection, spread through donor antigenic activity, and end with meticulous surgery. Prevention of corneal graft rejection lies with reduction of the donor antigenic tissue load, minimizing host and donor incompatibility by tissue matching and suppressing the host immune response. Management of corneal graft rejection consists of early detection and aggressive therapy with corticosteroids. Corticosteroid therapy, both topical and systemic, is the mainstay of management. Addition of immunosuppressive to the treatment regimen helps in quick and long term recovery. Knowledge of the immunopathogenesis of graft rejection may allow a better understanding of the immunological process thus helping in its prevention, early detection and management.

The new malononitrilamide immunosuppressant FK778 prolongs corneal allograft survival in the rat keratoplasty model

PURPOSE

Aim of this study was to prove the efficacy and safety of the new malononitrilamide immunosuppressive FK778 in prolonging clear graft survival following allogeneic orthotopic keratoplasty in rats.

METHODS

Sixty-seven penetrating keratoplasties were performed using Fisher and Lewis rats as donors and recipients, respectively: group 1 (n=11), allogeneic control without therapy; group 2 (n=12), syngeneic control; group 3 (n=11), mycophenolate mofetil (MMF) 40 mg/kg bodyweight; group 4 (n=12), FK778 5 mg/kg bodyweight; group 5 (n=12), FK778 10 mg/kg bodyweight; and group 6 (n=9), FK778 20 mg/kg bodyweight. Four animals in each group were killed for immunohistological evaluation on day 14. Therapy was administered orally for 18 days. The grafts were evaluated every three days by means of a scoring system including opacity, oedema, and vascularization. Time to rejection was analysed with the Kaplan-Meier survival analysis and compared with the log-rank test. The densities of infiltrating immune cells were compared statistically using the non-parametric Mann-Whitney test.

RESULTS

Mean rejection-free graft survival was 11.4 days in group 1 (allogeneic control), 100 days (total follow-up time) in group 2 (syngeneic control), 24.0 days in group 3 (MMF 40 mg/kg), 15.7 days in group 4 (FK778 5 mg/kg), 19.1 days in group 5 (FK778 10 mg/kg), and 25.4 days in group 6 (FK778 20 mg/kg) (P<0.005).

CONCLUSIONS

Systemic immunosuppression with FK778 prolongs graft survival in the rat keratoplasty model. FK778's efficacy is comparable with that of MMF in preventing immunologic graft rejection.

An open prospective pilot study on the use of rapamycin after penetrating high-risk keratoplasty

BACKGROUND

The purpose of this study was to prove efficacy and safety of systemic immunosuppression with rapamycin following penetrating high-risk keratoplasty. Rapamycin has shown its immunosuppressive potential in the rat keratoplasty model and is a component of several immunosuppressive protocols after solid organ transplantation. In this pilot study, we compared the efficacy and safety of rapamycin and mycophenolate mofetil (MMF).

METHODS

Ten patients (group 1) undergoing high-risk keratoplasty were included in this study, receiving rapamycin as postoperative immunoprophylaxis. Rapamycin was administered orally once daily (blood trough level 4-10 ng/ml) for 6 months. Thereafter, it was tapered over 2 weeks. The control group (group 2) consisted of 24 patients who received 1000 mg MMF twice daily for 6 months. All of the patients received postoperative medication with fluocortolone 1 mg/kg/day (tapered over 3 weeks) and prednisolone acetate eyedrops 5 times per day (tapered over 5 months).

RESULTS

Mean follow-up of all patients (n=34) was 739 days. No immune reaction was observed in groups 1 and 2 during the first 6 months under immunosuppression. Two immune reactions occurred in group 1, and five in group 2 within a 2-year follow-up. All of the immune reactions were reversible. The side effects observed in both groups were mostly reversible.

CONCLUSIONS

Rapamycin and mycophenolate mofetil seem to be similarly efficacious in preventing immune reactions after high-risk keratoplasty, as long as they are administered. However, we observed a broad spectrum of side effects from rapamycin.

Recommendations for Use of Everolimus After Heart Transplantation: Results From a Latin-American Consensus Meeting

Despite improvements during the last decades, heart transplantation remains associated with several medical complications, which limit clinical outcomes: acute rejection with hemodynamic compromise, cytomegalovirus (CMV) infections, allograft vasculopathy, chronic renal failure, and neoplasias. Everolimus, a proliferation signal inhibitor, represents a new option for adjunctive immunosuppressive therapy. Everolimus displays better efficacy in de novo heart transplant patients than azathioprine for prophylaxis of biopsy-proven acute rejection episodes of at least ISHLT grade 3A (P < .001), of allograft vasculopathy (P < .01), and of CMV infections (P < .01). These findings suggest that everolimus potentially play an important role as part of immunosuppressive therapy in heart transplant recipients. Heart transplant investigators from Latin America produced recommendations for everolimus use in daily practice based on available data and their own experience.

Systemic mycophenolate mofetil avoids immune reactions in penetrating high-risk keratoplasty: preliminary results of an ongoing prospectively randomized multicentre study

Recently, in a monocentre study mycophenolate mofetil (MMF) was demonstrated to be efficacious and safe in penetrating high-risk keratoplasty. Here, preliminary results of a randomized multicentre trial are presented. To date, 86 of 140 scheduled patients undergoing high-risk penetrating keratoplasty have already been randomized into the two study groups: 48 into the MMF group and 38 into the control group. All 86 patients received fluocortolon 1 mg/kg body weight/day, tapered within 3 weeks, and topical prednisolone acetate 1% tapered within 5 months. MMF was administered at a daily oral dose of 2 x 1000 mg for the first 6 postoperative months. Thereafter, MMF was tapered within 2 weeks. The proportion of grafts with immune reactions and side-effects were the main outcome measures. Within an average follow up of 9.2 +/- 6.6 months two patients developed reversible endothelial immune reactions in the MMF group after cessation of MMF application. In the control group, five reversible and three irreversible immune reactions were observed within an average follow up of 10.1 +/- 7.6 months. According to Kaplan and Meier analysis, the ratio of grafts without immune reactions was estimated 89% 1 year postoperatively in the MMF group, in contrast to only 67% in the control group (P = 0.03; log-rank test). Fifteen patients experienced side-effects, especially gastroenterotoxicity, tachycardia, arthralgia or systemic infections. All attributable side-effects were reversible. Systemic MMF may be an effective and safe immune modulating drug in the prophylaxis of immune reactions after penetrating high-risk keratoplasty.

Topical FK506 as immunoprophylaxis after allogeneic penetrating normal-risk keratoplasty: a randomized clinical pilot study

The purpose of this study was to evaluate for the first time the efficacy and safety of topical FK506 in patients undergoing penetrating normal-risk keratoplasty in a prospectively randomized clinical trial. Twenty patients were treated with FK506 0.06% three times per day for 6 months postoperatively. An additional 20 patients received five drops of prednisolone acetate 1% tapered within 6 months. All patients received 1 mg/kg bodyweight/day of systemic fluocortolon tapered within 3 weeks postoperatively. Clear graft survival, ratio of immune reactions and side effects were the main outcome measures. One year postoperatively all patients of the FK 506 group were free from immune reactions, in contrast to 84% in the steroid group (Kaplan-Meier values; P = 0.9 in the log rank test). None of the patients developed irreversible graft failure so far. In eight patients of the FK506 group premature withdrawal of the drug was deemed appropriate because of local side effects. FK506 might turn out to become an effective immunoprophylaxis in subjects undergoing penetrating normal-risk keratoplasty. Local discomfort should be further reduced.

Immunosuppression with cyclosporine A and mycophenolate mofetil after penetrating high-risk keratoplasty: a retrospective study

BACKGROUND

Graft-prognosis after penetrating high-risk keratoplasty has improved considerably with the use of systemic immunosuppressive medications. In this retrospective investigation we analyzed the long-term results of 417 high-risk keratoplasties with systemic immunosuppression (cyclosporine A [CsA] or mycophenolate mofetil [MMF]).

METHODS

A total of 417 high-risk keratoplasties with postoperative systemic immunosuppression were evaluated retrospectively: CsA has been given in 252 keratoplasties since 1987, aiming at blood trough levels of 120 to 150 ng/mL. Systemic MMF at a daily dose of 2 x 1 g was administered in 149 surgical procedures. After 16 high-risk keratoplasties, combined systemic immunosuppression with CsA and MMF was administered. Systemic immunosuppression was scheduled for 6 to 12 months. All patients received fluocortolone 1 mg/kg body weight per day, tapered over 3 weeks, and topical prednisolone acetate 1%, tapered over 5 months.

RESULTS

Rejection-free graft survival after 1 year was 75% in the CsA group and 89% in the MMF group; 60% of the grafts in the CsA group and 72% of the grafts in the MMF group were rejection-free 3 years postoperatively (Kaplan-Meier log-rank test P=0.03). Clear graft survival after 1 and 3 years was 92% and 77% (CsA) and 96% and 87% (MMF), respectively. The MMF-treated patients showed fewer side effects than the CsA-treated patients. The side effects attributable to both drugs were reversible.

CONCLUSIONS

We found a statistically significant, stronger effect of MMF compared with CsA in preventing immune reactions after high-risk keratoplasty, despite a shorter MMF administration compared with CsA. Both systemic immunosuppressants were shown to have comparable potency regarding clear graft survival and were well tolerated.

Prevention of corneal allograft rejection in a mouse model of high risk recipients

AIM

To determine the effectiveness of treatment with immunosuppressive drugs and monoclonal antibodies (mAb) after penetrating keratoplasty in two different models of high risk mouse recipients.

METHODS

Corneas were grafted orthotopically in mouse models of high risk recipients with either neovascularisation of the graft bed or presensitisation to graft donor antigens. Recipients were treated with mAb against CD4(+) or CD8(+) cells or against T cells, or were treated with cyclosporin A (CsA) or mycophenolate mofetil (MMF), or a combination of both drugs.

RESULTS

Control untreated recipients with neovascularised graft bed or presensitised to the graft donor antigens rejected corneal allografts in 12.5 (SD 2.3) and 9.9 (1.6) days, respectively. Treatment of graft recipients with a neovascularised graft bed with mAb anti-CD4 or anti-T cells, but not with mAb anti-CD8 or with immunosuppressive drugs, resulted in a significant prolongation of graft survival; 75% and 28.5%, respectively, of grafts survived for more than 45 days after grafting. However, none of the treatments were successful in presensitised recipients.

CONCLUSIONS

Treatment of high risk recipients with mAb anti-CD4 is more effective in preventing corneal allograft rejection than the treatment with mAb anti-CD8 or the immunosuppressive drugs MMF and CsA. However, the effectiveness of the treatment depends on the recipients' pretransplantation risk type.

Penetrating limbo-keratoplasty for granular and lattice corneal dystrophy

PURPOSE

To assess clinical follow-up data, and to identify donor epithelial cells after homologous penetrating central limbo-keratoplasty in patients with granular and lattice corneal dystrophies compared with patients who underwent conventional penetrating keratoplasty (PK).

DESIGN

Mixed retrospective and prospective nonrandomized comparative case series.

PARTICIPANTS AND CONTROLS

Twenty-six patients who underwent 33 limbo-keratoplasty procedures for granular or lattice corneal dystrophy since May 1995 and a historical control group of 24 patients who underwent 36 PK procedures between November 1986 and May 1995.

METHODS

Postoperatively, all but 2 limbo-keratoplasty patients were treated with systemic immunosuppressants for 6 months. All patients received long-term topical immune prophylaxis with prednisolone-21-acetate 1% (2 drops per day). After obtaining informed consent, epithelial cells were harvested from 10 limbo-keratoplasty eyes of 8 patients with granular dystrophy and 7 limbo-keratoplasty eyes of 7 patients with lattice dystrophy. Conjunctival epithelium or buccal mucosal epithelium for recipient identification and corneal epithelial cells from 3 graft sites were harvested. Deep-frozen donor corneoscleral rims were analyzed to characterize donor features. Genetic analysis was performed by polymerase chain reaction of short tandem repeat (STR) loci.

MAIN OUTCOME MEASURES

The ratio of dystrophy recurrences in the graft was clinically assessed. Donor features in epithelial cells were genetically established if at least 1 STR profile differed from that of the recipient.

RESULTS

There were 5 recurrences in limbo-keratoplasty eyes with granular dystrophy and 2 recurrences in limbo-keratoplasty eyes with lattice dystrophy, compared with 15 and 6 recurrences in PK eyes, respectively. The differences between limbo-keratoplasty and PK were not statistically significant over time (log-rank test; P = 0.14 for granular dystrophy and P = 0.56 for lattice dystrophy; alpha error, 0.05). For genetic analysis, 12 of 17 samples were evaluated. Donor epithelial cells were detected in 5 of the 12 samples (42%).

CONCLUSIONS

Limbo-keratoplasty tended to be associated with fewer recurrences of granular and lattice dystrophies. However, the difference was not yet statistically significant, probably due to the disappearance of the transplanted limbal stem cells over time. Genetic analysis confirmed the survival of transplanted limbal stem cells over several years in some limbo-keratoplasty eyes, which might correlate with less recurrence. Limbo-keratoplasty, therefore, is likely to represent a first step towards long-term recurrence-free survival of corneal grafts in patients with granular and lattice dystrophies.

Improvement of graft prognosis in penetrating normal-risk keratoplasty by HLA class I and II matching

BACKGROUND

Owing to contradictory results, HLA matching in penetrating keratoplasty still is equivocal. Different surgical techniques in multicentre studies, missing risk differentiation in high-risk situations, and faulty HLA typing can be identified as main reasons for these contradictory results. In this monocentre study, the value of HLA class I and II matching (A, B, DR loci) was examined in a homogeneous group of 418 normal-risk keratoplasty patients using serological typing techniques for HLA class I and immunogenetic typing techniques for class II.

METHODS

Penetrating normal-risk keratoplasty was performed in two groups of patients (group I with 0-2, group II with 3-6 mismatches in the A/B/DR loci). All surgery was carried out by three experienced surgeons according to a standardized scheme. Furthermore, postoperative therapy and controls were standardized. There were no statistically significant differences between the two study groups with regard to the number of ABO or H-Y compatibilities, patient age, patient gender, ratio of previous intraocular surgery, ratio of triple procedures, indication for surgery, follow-up period, donor age, donor gender, post-mortem time of the graft, and endothelial cell density of the graft at the end of organ culture. All HLA typing was performed in a quality-controlled laboratory, serologically for HLA class I (A and B loci) and immunogenetically for HLA class II (DR locus).

RESULTS

At 4 years postoperatively, the ratio of clear and rejection-free graft survival was 92% in group I and 66% in group II (Kaplan-Meier estimation, log rank test, P=0.03). Monovariate analysis in the Cox model gave no influence of solitary HLA class I or II matching, but only an influence of combined HLA class I and II matching (P=0.03).

CONCLUSIONS

In this monocentre study with proper typing techniques, the beneficial effect of HLA class I plus II matching on clear and rejection-free graft survival could be demonstrated in a homogeneous group of normal-risk keratoplasty patients.

Everolimus

Everolimus is an immunosuppressant that blocks growth factor-mediated proliferation of haematopoietic and nonhaematopoietic cells. Oral everolimus 0.75 or 1.5mg twice daily significantly reduced the incidence of the primary composite endpoint, efficacy failure 6 months after transplantation, compared with azathioprine 1-3 mg/kg/day, in adult cardiac transplant recipients. All patients also received baseline immunosuppression with cyclosporin and corticosteroids. The incidence of efficacy failure remained significantly lower in everolimus recipients than in those receiving azathioprine 1 and 2 years after cardiac transplantation. However, graft and patient survival rates at 1 year were similar in patients receiving everolimus or azathioprine. The incidence of graft vasculopathy 2 years after transplantation was significantly lower in cardiac transplant recipients receiving everolimus 0.75 mg twice daily than in those receiving azathioprine. The combined incidence of biopsy-confirmed acute rejection, graft loss, death, or loss to follow-up was similar in adult patients receiving everolimus 1.5 or 3 mg/day or mycophenolate mofetil (MMF) 2 g/day 1 or 3 years after renal transplantation. Patients also received baseline immunosuppression with cyclosporin and corticosteroids. Compared with azathioprine and MMF, everolimus is associated with a lower incidence of cytomegalovirus infection in cardiac and renal transplant recipients. Everolimus has been associated with thrombocytopenia, leucopenia and elevated serum lipids and creatinine.

Tratamiento con azitromicina en la fibrosis quística

Progressive lung disease, caused by chronic endobronchial colonization, is the major cause of morbidity and mortality in patients with cystic fibrosis (CF). Several pathogens, including Staphylococcus aureus and Pseudomonas aeruginosa are responsible for this effect. The steadily improving prognosis of CF has been attributed to the use of antibiotics with activity against these organisms. Despite a significant increase in the amount of published material demonstrating the potential role of macrolide antibiotics as antiinflammatory agents and their effects on bacterial virulence, their mechanism of action in CF patients is still unknown. Although there is a limited number of clinical trials assessing the efficacy and safety of azithromycin (AZM) in CF, increasing evidence suggests that 3 to 6-month AZM treatment in CF patients is safe and well tolerated. This treatment results in clinical improvement, decreasing the number of pulmonary exacerbations and increasing pulmonary function. Therefore, chronic treatment with AZM should be considered in CF patients added to conventional therapy. Clinical experience with macrolides other than AZM in CF patients is very limited.

Differential contribution of natural killer cells to corneal graft rejection in 3-week-old versus mature rats

BACKGROUND

The aim of this study was to compare immunologic graft rejection in adult and 3-week-old immature recipients in the rat keratoplasty model.

METHODS

Forty orthotopic penetrating keratoplasties were performed in four different donor-recipient combinations. Group 1 consisted of adult Fisher donors and adult Lewis recipients, group 2 consisted of adult Fisher donors and immature Lewis recipients, group 3 consisted of adult Lewis donors and recipients, and group 4 consisted of adult Lewis donors and immature Lewis recipients. An immunohistologic evaluation of the grafts was performed on day 14.

RESULTS

Grafts in both allogeneic groups (groups 1 and 2) showed infiltration with CD4+ cells, CD8+ cells, natural killer (NK) cells, interleukin-2-receptor+ cells, macrophages, and intercellular adhesion molecule-1+ cells. The density of infiltrating CD4+, CD8+, interleukin-2-receptor+, and intercellular adhesion molecule-1+ cells in the graft stroma, however, was statistically significantly lower in the immature group (group 2) than in the adult group (group 1). The density of CD161+ NK cells, in contrast, was statistically significantly higher in the immature group than in the adult group. There were no or only a few infiltrating inflammatory cells in grafts of both syngeneic groups (groups 3 and 4).

CONCLUSIONS

We were able to establish for the first time an animal model for keratoplasty in infants that showed that the mechanism of graft rejection in young recipients seems to be different from that in mature rats. In adult recipients, alloreactive T cells are the main mediators of rejection, whereas NK cells seem to play a more dominant role in immature recipients.

Recent developments in the pharmacological treatment and prevention of corneal graft rejection

At present, given the high initial success rate of corneal transplantation (although late survival is poor), immunosuppression is often reserved for 'high-risk' patients. Despite immune privilege, corneal graft rejection remains the leading cause of corneal allograft failure. Interpreting the limited and also restricted design of most trials, immunosuppressive therapy has not enjoyed the success seen in solid organ grafts. This review discusses the limited data available whilst proposing newer therapies that have developed as a result of our increased understanding of the immunobiology of corneal graft rejection.

Chronic endophthalmitis mimicking an endothelial immune reaction after penetrating keratoplasty

We describe a patient with chronic inflammation after combined penetrating keratoplasty and cataract surgery. This condition has been considered an unusual endothelial immune reaction. Cytopathological examination of the aqueous humor showed abundant neutrophil granulocytes, a few macrophages, and sparse lymphocytes. The predominance of neutrophil granulocytes but no macrophages or lymphocytes, as found in cases of an endothelial immune reaction, was interpreted as evidence of chronic endophthalmitis. Cytopathological evaluation of aqueous humor can be a helpful tool for differentiating between an endothelial immune reaction and chronic endophthalmitis after combined PKP and cataract surgery.