Immunoglobulins in the human cornea

Corneal Copper Deposition Secondary to Monoclonal Gammopathy in a Patient With Chronic Lymphocytic Leukemia: A Case Report

Hypercupremia-induced corneal copper deposition secondary to monoclonal gammopathy is rare and shows a characteristic corneal opacity quite different from other causes of hypercupremia, such as Wilson's disease. This report describes a case of corneal copper deposition in a patient with monoclonal gammopathy associated with chronic lymphocytic leukemia. An 84-year-old man with slowly progressive corneal opacity was referred to our hospital. The corneal opacity was present at least five years ago. The patient's best-corrected visual acuity was 20/25 OU (in both eyes) at the initial visit to our hospital. Slit-lamp examination and anterior segment optical coherence tomography revealed bilateral brown-colored opacity localized to deep layers of the central cornea. In vivo confocal microscopy (IVCM) showed indistinct corneal stromal cells in the deep layer and endothelial cells. The possible differential diagnoses were corneal dystrophy and Wilson's disease, but the color, shape, or site of corneal opacity was inconsistent with the disease. As the patient had a history of chronic lymphocytic leukemia, which is often associated with monoclonal gammopathy, we suspected that the corneal opacity was copper deposition in association with the hematologic diseases. Laboratory examinations showed elevated serum copper and normal ceruloplasmin. Serum protein electrophoresis revealed significantly high IgG levels with depression of IgA, IgE, and IgM. These results supported our diagnosis. Followingly, we consulted the patient's attending hematologist, and the doctor initiated treatment for hypercupremia. In conclusion, hypercupremia secondary to monoclonal gammopathy should be considered a possible cause of central brown-colored corneal opacity.

Immunohistochemical staining of immunoglobulin G in healthy equine, canine, and feline corneas

Objective

Establishing an immunohistochemical approach for semi‐quantitative assessment of the presence of immunoglobulin G (IgG) in equine, canine, and feline corneas.

Procedures

Healthy corneas of horses, dogs, and cats, euthanized because of a fatal disease or an unrecoverable trauma unrelated to and without a history of ophthalmic disease were formalin‐fixed, paraffin‐embedded, and determined to be pathomorphologically healthy by light microscopy. Automated immunohistochemistry was performed using primary antibodies against IgG, biotin‐conjugated secondary antibodies, and streptavidin‐peroxidase, as well as diaminobenzidine for visualization. After counterstaining with hematoxylin, epithelium, stroma, Descemet´s membrane (DM), and endothelium were semi‐quantitatively scored for the presence of IgG on a 4‐grade scale (0 = no, 1 = faint, 2 = medium, 3 = strong staining) by light microscopy.

Results

Corneal specimens of 20 horses (40 eyes) with a median age of 15.5 years (range 2–31 years), 12 dogs (21 eyes) with a median age of 10.0 years (range 4–16), and 13 cats (24 eyes) with a median age of 10.0 years (range 2–18) were included in the study. Different sexes and breeds were represented. In all corneas (100%), significant medium signal intensity in the stroma was observed. Variable immunosignal was obtained in epithelium, DM, and endothelium.

Conclusion

This method reproducibly allows for the detection of IgG in healthy equine, canine, and feline corneas, particularly stroma. Semi‐quantitative results evidence medium presence of IgG in the corneal stroma. Further research is needed to evaluate IgG presence in diseased corneas.

Peripheral ulcerative keratitis

Peripheral ulcerative keratitis (PUK) is an inflammatory condition of the peripheral cornea with hallmark features of epithelial defects and stromal destruction as a result of a complex interplay of factors including host autoimmunity and the peculiar anatomic and physiologic features of the peripheral cornea and environmental factors. PUK may be the result of local or systemic causes and infectious or noninfectious causes. Arriving at a specific etiological diagnosis requires a meticulous clinical workup that may include a battery of laboratory and radiological investigations. Management by a team of internists or rheumatologists and ophthalmologists and judicious use of immunosuppressive agents may yield favorable results minimizing adverse effects. We review current clinical knowledge on the diagnosis and management of PUK.

The Neonatal Fc Receptor and Complement Fixation Facilitate Prophylactic Vaccine-Mediated Humoral Protection against Viral Infection in the Ocular Mucosa

The capacity of licensed vaccines to protect the ocular surface against infection is limited. Common ocular pathogens, such as HSV-1, are increasingly recognized as major contributors to visual morbidity worldwide. Humoral immunity is an essential correlate of protection against HSV-1 pathogenesis and ocular pathology, yet the ability of Ab to protect against HSV-1 is deemed limited due to the slow IgG diffusion rate in the healthy cornea. We show that a live-attenuated HSV-1 vaccine elicits humoral immune responses that are unparalleled by a glycoprotein subunit vaccine vis-à-vis Ab persistence and host protection. The live-attenuated vaccine was used to assess the impact of the immunization route on vaccine efficacy. The hierarchical rankings of primary immunization route with respect to efficacy were s.c. ≥ mucosal > i.m. Prime-boost vaccination via sequential s.c. and i.m. administration yielded greater efficacy than any other primary immunization route alone. Moreover, our data support a role for complement in prophylactic protection, as evidenced by intracellular deposition of C3d in the corneal epithelium of vaccinated animals following challenge and delayed viral clearance in C3-deficient mice. We also identify that the neonatal Fc receptor (FcRn) is upregulated in the cornea following infection or injury concomitant with increased Ab perfusion. Lastly, selective small interfering RNA-mediated knockdown of FcRn in the cornea impeded protection against ocular HSV-1 challenge in vaccinated mice. Collectively, these findings establish a novel mechanism of humoral protection in the eye involving FcRn and may facilitate vaccine and therapeutic development for other ocular surface diseases.

A Highly Efficacious Herpes Simplex Virus 1 Vaccine Blocks Viral Pathogenesis and Prevents Corneal Immunopathology via Humoral Immunity

Correlates of immunologic protection requisite for an efficacious herpes simplex virus 1 (HSV-1) vaccine remain unclear with respect to viral pathogenesis and clinical disease. In the present study, mice were vaccinated with a novel avirulent, live attenuated virus (0ΔNLS) or an adjuvanted glycoprotein D subunit (gD-2) similar to that used in several human clinical trials. Mice vaccinated with 0ΔNLS showed superior protection against early viral replication, neuroinvasion, latency, and mortality compared to that of gD-2-vaccinated or naive mice following ocular challenge with a neurovirulent clinical isolate of HSV-1. Moreover, 0ΔNLS-vaccinated mice exhibited protection against ocular immunopathology and maintained corneal mechanosensory function. Vaccinated mice also showed suppressed T cell activation in the draining lymph nodes following challenge. Vaccine efficacy correlated with serum neutralizing antibody titers. Humoral immunity was identified as the correlate of protection against corneal neovascularization, HSV-1 shedding, and latency through passive immunization. Overall, 0ΔNLS affords remarkable protection against HSV-1-associated ocular sequelae by impeding viral replication, dissemination, and establishment of latency.

IMPORTANCE

HSV-1 manifests in a variety of clinical presentations ranging from a rather benign "cold sore" to more severe forms of infection, including necrotizing stromal keratitis and herpes simplex encephalitis. The present study was undertaken to evaluate a novel vaccine to ocular HSV-1 infection not only for resistance to viral replication and spread but also for maintenance of the visual axis. The results underscore the necessity to reconsider strategies that utilize attenuated live virus as opposed to subunit vaccines against ocular HSV-1 infection.

Ocular Mucosal Immunity

Mucosal immunity defends the ocular surface against antigenic challenge and microbial invasion. The principal effector site is the lacrimal gland, where immunoglobulin A (IgA) antibodies are produced. Nasal-associated lymphoid tissue and posterior cervical lymph nodes function as major inductive sites for tear IgA responses. Neural connections and systemic hormones maintain the integrity and function of the ocular surface. Neuroenzyme activities in the lacrimal gland are influenced by ocular infections, leading to reduced expression of acetylcholine and modulation of receptors on acinar cells and on plasma cells, thereby decreasing fluid and immunoglobulin secretion. T lymphocyte-dependent responses result in production of interleukin-4 in lacrimal glands, thereby influencing cholinergic enzyme activity affecting immune processes and lacrimal physiology. Furthermore, neuropeptides released into lymphoid structures or inflamed tissues are chemotactic for antigen-presenting cells and affect their interactions with T cells. Thus, in developing therapeutic approaches for treating dry-eye conditions and vaccination strategies to elicit protective ocular mucosal immune responses, the entire lacrimal functional unit should be considered.

Update on peripheral ulcerative keratitis

Ulcerative inflammation of the cornea occurs in the perilimbal cornea, and is associated with autoimmune collagen vascular and arthritic diseases. Rheumatoid arthritis is the most frequent underlying disease. The tendency for peripheral location is due to the distinct morphologic and immunologic characteristics of the limbal conjunctiva, which provides access for circulating immune complexes to the peripheral cornea via the capillary network. Deposition of immune complexes in the terminal ends of limbal vessels initiates immune-mediated vasculitis, and causes inflammatory cell and protein leakage due to vessel wall damage. Development of peripheral ulcerative keratitis associated with systemic disease may represent worsening of a potentially life-threatening disease. Accompanying scleritis, particularly the necrotizing form, is usually observed in severe cases, which may result in corneal perforation and loss of vision. Although first-line treatment with systemic corticosteroids is indicated for acute phases, immunosuppressive and cytotoxic agents are required for treatment of peripheral ulcerative keratitis associated with multisystem disorders. Recently, infliximab, a chimeric antibody against proinflammatory cytokine tumor necrosis factor-alpha, was reported to be effective in cases refractory to conventional immunomodulatory therapy. The potential side effects of these therapies require close follow-up and regular laboratory surveillance.

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.

Tissue crossmatch before corneal transplantation

AIM

To investigate the influence of anticorneal antibodies on the outcome of transplantation in recipients before penetrating keratoplasty.

METHODS

100 consecutive penetrating keratoplasties performed between July 1995 and June 1996 were included in this study. Donor corneoscleral rim cryosections were incubated with recipient serum. Fixation of recipient IgM on donor corneas was revealed with a polyclonal anti-human mu-chain antibody. The mean follow up time was 61 months. Five years after transplantation, 63% of patients were available for follow up. During the follow up period, 15% of keratoplasties failed because of irreversible rejection.

RESULTS

Anti-donor stromal lamellae IgM were found in 14 recipients. Anti-donor keratocyte IgM were present in 28 recipients. Dilution of recipient serum (up to 1/800) did not modify the results of positive crossmatch assays. Crossmatch assays performed with positive recipient sera and negative donor corneoscleral rims were negative. No significant influence of IgM crossmatch results on graft survival and rejection-free graft survival was found.

CONCLUSION

Donor specific anticorneal stroma IgM were found in 28% of recipients before transplantation. This pre-immunisation was not associated with a higher risk of transplantation rejection.

Annular crystalline keratopathy in association with immunoglobulin therapy for pyoderma gangrenosum

PURPOSE

To report on a patient with a clinical presentation of annular crystalline keratopathy after immunoglobulin therapy for pyoderma gangrenosum.

METHODS

Case report of a 6-year-old boy with biopsy-proven history of pyoderma gangrenosum who had undergone several cycles of systemic immunoglobulin therapy. The literature on ocular manifestations associated with pyoderma gangrenosum was reviewed.

RESULTS

One year after the last cycle, the patient complained of the sudden onset of photophobia. Slit-lamp biomicroscopy revealed bilateral symmetric crystalline deposits in an annular region of the cornea. Because visual acuity was not reduced, specific therapy was not initiated. Symptoms could be reduced by the prescription of medical edged filter lenses.

CONCLUSIONS

Annular crystalline corneal deposits may be associated with immunoglobulin therapy or represent a hitherto unknown ocular complication of pyoderma gangrenosum.

A dominant role for Fc gamma receptors in antibody-dependent corneal inflammation

Although production of specific Ab is a critical element of host defense, the presence of Ab in tissues leads to formation of immune complexes, which can trigger a type III Arthus reaction. Our studies on a mouse model of river blindness showed that Ab production is essential for recruitment of neutrophils and eosinophils to the cornea and for development of corneal opacification. In the current study, we determined the relative contribution of complement and FcgammaR interactions in triggering immune complex-mediated corneal disease. FcgammaR(-/-) mice, C3(-/-) mice, and immunocompetent control (B6/129Sj) mice were immunized s.c. and injected intrastromally with Onchocerca volvulus Ags. Slit lamp examination showed that control mice, C3(-/-) mice, and control mice injected with cobra venom factor developed pronounced corneal opacification, whereas corneas of FcgammaR(-/-) mice remained completely clear. Furthermore, recruitment of neutrophils and eosinophils to the corneal stroma was significantly impaired in FcgammaR(-/-) mice, but not in C3(-/-) mice or cobra venom factor-treated mice. We therefore conclude that FcgammaR-mediated cell activation, rather than complement activation, is the dominant pathway of immune complex disease in the cornea. These findings demonstrate a novel role for FcgammaR interactions in mediating ocular inflammation.

Immune mechanisms in Onchocerca volvulus-mediated corneal disease (river blindness)

Infection with the parasitic nematode Onchocerca volvulus can lead to severe visual impairment and blindness. In an effort to characterize the molecular basis for the inflammatory response in the cornea, we have developed a murine model for O. volvulus-mediated keratitis in which parasite antigens are injected into the corneal stroma of sensitized mice. This model reproduces the two main clinical features of human disease, corneal opacification and neovascularization. Histological analysis of corneas from these mice reveals a biphasic recruitment of neutrophils and eosinophils to the central cornea, along with a small, but persistent number of CD3+ cells. In this review, we present evidence that production of antigen-specific T cell and antibody responses are essential for development of O. volvulus keratitis, and we propose a sequence of molecular and cellular events that lead to migration of inflammatory cells to the cornea and to loss of corneal clarity.

Twenty-five-year panorama of corneal immunology: emerging concepts in the immunopathogenesis of microbial keratitis, peripheral ulcerative keratitis, and corneal transplant rejection

PURPOSE

To describe the most recent advances in our understanding of the cellular and molecular mechanisms involved in the immunopathogenesis of corneal immunoinflammatory disorders including microbial keratitis, peripheral ulcerative keratitis. and allograft rejection.

METHODS

Review of the published peer-reviewed literature that has contributed significantly to our modern understanding of corneal immunology. In addition, the authors have summarized the information in conceptual diagrams that highlight the critical cellular and molecular pathways that lead to corneal immune responses in the two most thoroughly studied corneal immune disorders, herpes simplex keratitis (HSK) and transplant rejection.

RESULTS

In spite of the wide array of molecular and cellular factors that mediate corneal immunity, critical mechanistic facets are shared by the various corneal immunoinflammatory disorders. These include activation and migration of local antigen-presenting cells (APCs), including Langerhans cells (LCs), upregulation in pleiotropic proinflammatory cytokines such as interleukin-1 (IL-1) and tumor necrosis factor-alfa (TNF-alpha) that can mediate a wide array of immune functions in addition to up-regulating protease expression. and chemokines that play a critical role on the one hand in attracting nonantigen-specific inflammatory cells such as neutrophils and on the other in attracting CD4+ T helper type 1 (Th1) cells that mediate most of the destruction in the cornea.

CONCLUSIONS

In the last 25 years, we have seen our field develop from a descriptive stage into a new phase where the fundamental processes that mediate and effect corneal immunity are being accurately deciphered. It is anticipated that this new knowledge will allow development of specific molecular and genetic therapeutic strategies that could target critical steps in the immunopathogenesis of disease without the untoward side-effects of nonspecific generalized immune suppression that still remains the standard of care today.

An Essential Role for Antibody in Neutrophil and Eosinophil Recruitment to the Cornea: B Cell-Deficient (μMT) Mice Fail to Develop Th2-Dependent, Helminth-Mediated Keratitis

Invasion of the corneal stroma by neutrophils and eosinophils and subsequent degranulation disrupts corneal clarity and can result in permanent loss of vision. In the current study, we used a model of helminth-induced inflammation to demonstrate a novel role for Ab in mediating recruitment of these inflammatory cells to the central cornea. C57BL/6 and B cell-deficient (μMT) mice were immunized s.c. and injected intrastromally with Ags from the parasitic helminth Onchocerca volvulus (which causes river blindness). C57BL/6 mice developed pronounced corneal opacification, which was associated with an Ag-specific IL-5 response and peripheral eosinophilia, temporal recruitment of neutrophils and eosinophils from the limbal vessels to the peripheral cornea and subsequent migration to the central cornea. In contrast, the corneas of μMT mice failed to develop keratitis after intrastromal injection of parasite Ags unless Ags were injected with immune sera. Eosinophils were recruited from the limbal vessels to the peripheral cornea in μMT mice, but failed to migrate to the central cornea, whereas neutrophil recruitment was impaired at both stages. With the exception of IL-5, T cell responses and peripheral eosinophils were not significantly different between C57BL/6 and μMT mice. Taken together, these findings not only demonstrate that Ab is required for the development of keratitis, but also show that recruitment of neutrophils to the cornea is Ab-dependent, whereas eosinophil migration is only partially dependent upon Ab interactions.

Vasculitic peripheral ulcerative keratitis

The onset of peripheral ulcerative keratitis in the course of a connective tissue disorder, such as rheumatoid arthritis, relapsing polychondritis, or systemic lupus erythematosus, may reflect the presence of potentially lethal systemic vasculitis. Moreover, peripheral ulcerative keratitis may be the first sign of systemic necrotizing vasculitis in patients with Wegener's granulomatosis, polyarteritis nodosa, microscopic polyangiitis, or Churg-Strauss syndrome. Although the exact pathogenesis of this severe corneal inflammation and destruction is not well understood, evidence points to a dysfunction in immunoregulation with immune complexes formed in response to autoantigens or to some unknown microbial antigen depositing in scleral and limbal vessels. These events lead to changes that are mainly responsible for the resulting tissue damage. In pauci-immune vasculitides positive for antineutrophil cytoplasmic antibodies, cell-mediated cytotoxicity may play an important role in the pathogenesis of peripheral ulcerative keratitis. Untreated systemic conditions such as those mentioned above may carry a grave prognosis for the eye and may also be life-threatening. Immunosuppressive therapy with corticosteroids and cytotoxic agents is, we believe, mandatory in the treatment of these multisystem disorders associated with vasculitic peripheral ulcerative keratitis.

The non-uniform distribution of albumin in human and bovine cornea

In our previous studies, we noted a non-uniform distribution of protein tracer preferentially entering the anterior stromal lamellae of the cornea from the limbus. Given other differences reported previously between the anterior and posterior lamellae of the cornea, and the number of corneal disorders in which abnormalities are preferentially confined to either the anterior or posterior lamellae, we were prompted to examine the distribution of albumin in normal human and bovine cornea. The distribution of albumin in bovine and human cornea was studied immunohistochemically. Total soluble protein and albumin in the anterior 1/3 and posterior 2/3 of the central, middle and peripheral cornea of bovine eyes was measured biochemically. To aid in interpreting the findings, a theoretical model was developed based upon the combined effects of diffusive and convective transport. Using immunohistochemical methods, in both bovine and human eyes, intense staining of albumin was found in the anterior 1/3 of the corneal stroma. There was a gradual reduction in staining intensity from the limbus to the central cornea in the anterior corneal stroma. Less staining was found in the posterior 2/3 of corneal stroma. Additionally, a greater concentration of soluble protein and albumin was found in the anterior stroma than in the posterior stroma of the bovine eyes by biochemical analyses. The theoretical model demonstrated that this distribution of protein required a difference in excluded volume fraction between the anterior and posterior stroma and was consistent with a convective flux originating at the limbus and passing through the corneal stroma. The soluble proteins of the bovine and human cornea are preferentially concentrated in the anterior cornea and near the limbus. This distribution is likely due to differences in excluded volume fraction between the anterior and posterior stroma and a small convective flux passing through the cornea.

Intracorneal bovine albumin: an immunologic model of corneal angiogenesis

BACKGROUND

We characterized the neovascularization that follows the intracorneal injection of bovine albumin (BA) in rabbits as a model of corneal angiogenesis.

METHODS

New Zealand white rabbits received intracorneal injections of phosphate-buffered saline with and without various amounts of BA. The rabbits were co-sensitized or pre-sensitized by intramuscular BA or were not sensitized. The corneal vascular response was quantified by ranking photographs taken periodically after the injection.

RESULTS

In pre-sensitized animals, blood vessels were apparent within 4 days and reached maximum intensity 14 days after the intracorneal injection. Corneas also vascularized in non-sensitized rabbits, but a larger dose (> 0.2 mg BA) was required than in pre-sensitized animals (> 0.02 mg BA). Vascularization began later in non-sensitized animals and was less extensive than in pre-sensitized animals.

CONCLUSION

The intracorneal injection of BA is a reproducible model of corneal angiogenesis in rabbits and should allow the involved immunological mechanisms to be elucidated.

Excimer phototherapeutic keratectomy for corneal subepithelial cryoglobulin deposits

A 64-year-old man with a history of cryoglobulinemia and repeated scraping of immunoglobulin deposits from both superficial corneas presented with gradual decrease in vision and progressive hyperopia caused by circumferential redeposition of the cryoglobulins in his corneas. He had debridment of the deposits combined with phototherapeutic keratectomy to smooth the corneal surface. Visual acuity and reading capacity markedly improved, and hyperopia regressed by 5.75 diopters (D) in the right eye and 5.25 D in the left. Follow-up was 3 years.

Paraproteinemic crystalloidal keratopathy: an ultrastructural study of two cases, including immunoelectron microscopy

The ultrastructural appearances of corneal crystalloidal deposits are described in two patients with an IgG-kappa paraproteinemia of uncertain pathogenesis. The crystalloids in one patient were overwhelmingly intracellular and were found mainly in stromal keratocytes, but also in basal corneal epithelial cells and the limbal vascular endothelium. Four types of crystalloid or immunoprotein-containing granules were recognizable in this case: 1) fibrillary crystalloids with a curvilinear filamentous substructure; 2) angulated geometric crystalloids that often had a linear filamentous substructure and transverse or oblique periodicity; 3) cordlike crystalloids; and 4) lysosomelike granules with amorphous contents. Immunoelectron microscopy demonstrated that all of these structures labeled for kappa-light chains, and rectangular type 2 crystalloids showed approximately a twofold greater concentration of the colloidal gold probe than the type 1 fibrillary crystalloids. The evidence suggested development of the crystalloids within lysosomes, with a progression from the granules containing amorphous material, through fibrillary crystalloids, to the geometric structures. The circumferential distribution of the corneal deposits, as well as the presence of vascular endothelial crystalloids and reduplication of external laminae around limbal blood vessels, suggests that the crystalloids originated predominantly or entirely from the blood, with transport of immunoprotein across damaged limbal microvasculature. The abnormal vasculature may also have contributed to corneal edema, which in turn may have exacerbated corneal opacification. The crystalloidal deposits in the other case were exclusively extracellular; they were located beneath and between corneal basal epithelial cells, and predominantly as a mantle around individual keratocytes. The crystalloids in this case consisted overwhelmingly of thick-walled tubules about 40 nm in diameter that labeled for both kappa-light chains and gamma chains with the colloidal gold immunoprobe. In addition, lucent vesicles within keratocytes were found only in sections labeled for kappa-light chains and were positive. The factors that might contribute to the formation of corneal crystalloidal deposits in immunoproliferative disorders are discussed, and include: 1) an inherent propensity for crystallization of some immunoglobulins or kappa-light chains, perhaps because of abnormal molecular structure; and 2) local factors in the cornea that might promote deposition and crystallization of immunoprotein, such as temperature, pH, the water content, and extracellular matrix components.

Diffusion of immunoglobulins into rabbit cornea after subconjunctival injection: experimental demonstration and mathematical model

To determine whether immunoglobulins of the IgG class diffus up to the corneal center after subconjunctival injection, rabbits were injected with fluorescein-isothiocyanate-labeled human IgG. The inoculum diffused from the entire periphery centrepetally towards the corneal center. The progression of the diffusion front slowed down as the distance to the limbus increased. The first increase of fluorescence in the corneal center was observed on day 6. The intensity increased during the following 10 days despite resorption in the corneal periphery due to the flow of IgG from paracentral toward central areas. The diffusion coefficient of 0.003-0.004 cm2/day was calculated by computer simulation using Fickian diffusion equations adapted for corneal geometry. We conclude that after subconjunctival application, IgG diffuses up to the corneal center with a delay of several days and that the penetration speed decreases as the distance to the limbus increases. This kinetics contributes to our understanding of the role of IgG in corneal pathology and may help to design therapeutic schedules for immunotherapy with IgG.

Corneal subepithelial monoclonal kappa IgG deposits in essential cryoglobulinaemia

A 60-year-old man suffering from photophobia and visual disturbances was found to have bilateral superficial corneal grey-white gelatinous deposits. An abnormal cold-precipitable serum component was found and characterised as homogeneous IgG-kappa immunoglobulin. Corneal immunohistochemical examination revealed subepithelial IgG-kappa deposits, focally replacing Bowman's layer. The patient underwent superficial keratectomy in both eyes with satisfactory visual results.

Serum antibody and ocular responses to murine corneal infection caused by Pseudomonas aeruginosa

The serum antibody response and differential corneal response to primary and secondary infections by Pseudomonas aeruginosa were investigated in DBA/2J (resistant) and C57BL/6J (susceptible) mice, since they respond differently to intracorneal challenge. Using an enzyme-linked immunosorbent assay, we found that naturally resistant DBA/2J mice mounted a significant immunoglobulin M (IgM) and IgG response to P. aeruginosa within 7 days postinfection of one eye; this was subsequently followed by a drop in the IgM response. Of 31 mice, 30 were able to restore corneal clarity within 3 to 4 weeks. However, when C57BL/6J mice were infected intracorneally, their levels of serum antibody developed more slowly than did those of the DBA/2J mice, and they were unable to restore corneal clarity within 8 to 12 weeks. None of the mice from either test strain mounted a detectable serum IgA response to P. aeruginosa over a 90-day holding period. However, infection of the contralateral, normal cornea of mice of both test strains resulted in a heightened IgG response to P. aeruginosa within 30 days after the secondary infection. Many (50%) of the susceptible C57BL/6J mice recovered or exhibited less severe corneal damage within the 30-day holding period. If the C57BL/6J mice were reinfected 60 days after the primary infection instead of after 30 days, most (89%) of the mice had restored corneal clarity within 3 to 6 days. Passive transfer of immune serum from either recovered DBA/2J or C57BL/6J mice to naive C57BL/6J mice resulted in the restoration of corneal clarity in many of the recipients following infection.

Evidence for a feline reservoir for dysgonic fermenter 2 keratitis

A 78-year-old female developed microbial keratitis from which corneal scrapings grew dysgonic fermenter 2. The infection initially responded poorly to a combination of topical antibiotics and corticosteroids but healed with intensive antibiotic therapy. There was no systemic predisposition to infection, and only feline exposure had occurred. Close association with a cat probably contaminated the eye.

Inflammatory diseases of the peripheral cornea

Immunologic differences exist between the peripheral and central cornea. The peripheral cornea is closer to the conjunctiva, which has all of the immunologic machinery necessary to generate an immune response. The peripheral cornea has more Langerhans' cells and IgM than the central cornea. The peripheral cornea also has more C1, the recognition unit of the classic pathway of complement, than the central cornea so that antigen-antibody complexes, whether formed in the cornea itself or whether derived from the tears, aqueous humor, or limbal vessels, may activate complement more effectively in the peripheral than central cornea. Autoimmune diseases that involve the peripheral cornea include Mooren's ulcer and collagen vascular diseases. The humoral- and cell-mediated autoimmune phenomena that are associated with Mooren's ulcer and its response to immunosuppressive therapy suggest that it is an autoimmune disease directed against the cornea itself. Collagen vascular diseases may be associated with peripheral corneal ulcers with or without scleritis. In these diseases, circulating immune complexes may lodge in the limbal vasculature causing an immune vasculitis or deposit in the peripheral cornea setting off the complement cascade. Peripheral corneal diseases that probably represent a hypersensitivity reaction to exogenous antigens include catarrhal infiltrates and ulcers and phlyctenules. In the United States today, these corneal lesions are generally associated with staphylococcal blepharitis. Experimental models suggest that hypersensitivity to Staphylococcus aureus cell wall antigens may be important to their immunopathogenesis.

Peripheral corneal disorders

The peripheral cornea is anatomically and physiologically distinct from its central counterpart. The major differences relate to the gradual transition of corneal tissues to those of the conjunctiva, episclera, and sclera; furthermore, the vascular structures, lymphatics, and inflammatory cells from these neighboring structures are intimately associated with the limbus and periphery of the cornea. The peripheral cornea is thereby predisposed to three main classes of disorders which do not normally involve the central cornea. First, local conditions affecting the sclera and conjunctiva may secondarily spread to involve the limbus and peripheral cornea. These include several infectious diseases, as well as hypersensitivity conditions, mass lesions, and degenerations. Second, due to the associated blood vessels and lymphatics, the peripheral cornea may be involved in a variety of systemic diseases, including vasculitides, autoimmune disorders, and abnormal metabolic conditions. Finally, there are several conditions, such as the noninflammatory peripheral degenerations, which primarily affect the peripheral cornea without associated ocular or systemic changes. In this review, we present a classification and discussion of the various disorders which may involve the peripheral cornea.

Relationship between proteases and descemetocele formation in experimental Pseudomonas keratitis

Proteases are involved in the pathogenesis of Pseudomonas aeruginosa infections of the cornea. Although there are many potential roles for these enzymes, involvement in corneal stroma destruction with subsequent descemetocele formation and/or corneal perforation is an important example. This study examined the relationship of elastase and alkaline protease to corneal destruction as indicated by descemetocele formation. The protease content of the overnight Mueller-Hinton broth cultures of various strains of P. aeruginosa correlated with the production of descemetoceles both in the rabbit trauma model of Pseudomonas keratitis and upon intrastromal injection of filtrates of the overnight culture media. The levels of alkaline protease correlated better with descemetocele formation than those of elastase. The influx of inflammatory cells was not correlated with descemetocele formation within 24 to 48 hrs.

Immunological concepts and the eye: a review of the classical and ocular arthus reactions

Inflammatory processes can involve any tissue in the eye. Despite advances in therapy, the sequelae of inflammation continue to be a major cause of visual impairment. Knowledge of disease pathogenesis in clinical ocular inflammations remains imprecise, and defined models are crucial in developing this understanding and evolving rational approaches to treatment. This review analyzes the contributions that studies of the classical and Arthus ocular Arthus-type reactions have made as to how the eye functions as an immunological entity. The anticipated development of therapeutic agents that may modulate immune processes with remarkable specificity, gives a new impetus to such experimental studies.

Ocular manifestations of multiple myeloma, Waldenström's macroglobulinemia and benign monoclonal gammopathy

Multiple myeloma, Waldenström's macroglobulinemia and benign monoclonal gammopathy are examples of diseases in which there is an uncontrolled proliferation of cells involved in antibody synthesis. Myeloma and macroglobulinemia are considered malignant diseases, whereas monoclonal gammopathy is benign or possibly a pre-myelomatous condition. Following a brief review of the immunoglobulins the various clinical manifestations of these disorders are described. The ophthalmic signs of these disorders can be seen in every ocular structure.

Phlyctenular keratoconjunctivitis

There is growing evidence that a variety of corneal disorders may be expressions of altered immune mechanisms. Phlyctenular keratoconjunctivitis is probably such a condition. Typically described as arising from hypersensitivity to tuberculin protein, other antigens clearly may participate, particularly staphylococcus products. When corneal involvement occurs, it need not be confined to the peripheral cornea. The symptoms of the process may be disproportionate to obvious findings and so exaggerated as to suggest a psychiatric disorder. Resultant visual deficits, if the disease is corneal, progressive, unrecognized, and untreated may be profound. Representative examples of this disease are cited. Immune mechanisms are reviewed. The importance of recognizing the characteristic sign and symptom complex is stressed. Appropriate diagnostic studies and treatment regimens are presented.

Peripheral corneal degeneration and occlusive vasculitis in Wegener's granulomatosis

A 61-year-old white woman, who had progressive arthritis over a two-year period, developed bilateral peripheral corneal degeneration. The superior cornea thinned to a thickness of approximately two thirds of normal. She died suddenly in the hospital and a primary occlusive vasculitis of the anterior ciliary arteries within the superior rectus muscles was found. There was necrotizing arteritis in the lungs, kidneys, adrenal caps, spleen, fallopian tubes, and skeletal muscle. The observation of an occlusive vasculitis of the anterior ciliary arteries in this patient supports the belief that ischemia may play a major role in peripheral marginal degeneration of the cornea.

Central corneal abscess

Central corneal abscess developed in the experimental animal after inoculation of biologically active staphylococcal strains in a paracentral epithelial lesion of the cornea. These abscesses did not ulcerate, developed only with high inocula, occurred more frequently in immunized rabbits. A serpiginous type of ulceration did not develop at the site of the initial epithelial lesion nor at any other place in the cornea. Histologically, the lesions consisted of densely packed polymorphonuclear leukocytes between the corneal lamellae.