Fc receptors in corneal epithelium

Ocular adverse events associated with antibody-drug conjugates used in cancer: Focus on pathophysiology and management strategies

Antibody-drug conjugates (ADCs) are designed to maximize cancer cell death with lower cytotoxicity toward noncancerous cells and are an increasingly valuable option for targeted cancer therapies. However, anticancer treatment with ADCs may be associated with ocular adverse events (AEs) such as dry eye, conjunctivitis, photophobia, blurred vision, and corneal abnormalities. While the pathophysiology of ADC-related ocular AEs has not been fully elucidated, most ocular AEs are attributed to off-target effects. Product labelling for approved ADCs includes drug-specific guidance for dose modification and management of ocular AEs; however, limited data are available regarding effective strategies to minimize and mitigate ocular AEs. Overall, the majority of ocular AEs are reversible through dose modification or supportive care. Eye care providers play key roles in monitoring patients receiving ADC therapy for ocular signs and symptoms to allow for the early detection of ADC-related ocular AEs and to ensure the timely administration of appropriate treatment. Therefore, awareness is needed to help ophthalmologists to identify treatment-related ocular AEs and provide effective management in collaboration with oncologists as part of the patient's cancer care team. This review provides an overview of ocular AEs that may occur with approved and investigational ADC anticancer treatments, including potential underlying mechanisms for ADC-related ocular AEs. It also discusses clinical management practices relevant to ophthalmologists for prevention, monitoring, and management of ADC-related ocular AEs. In collaboration with oncologists, ophthalmologists play a vital role in caring for patients with cancer by assisting with the prompt recognition, mitigation, and management of treatment-related ocular AEs.

The presence of keratin 5 as an IgG Fc binding protein in human corneal epithelium

Rabbit immunoglobulin G (IgG) binds specifically to the human corneal epithelium. We investigated this phenomenon to identify the binding material in the tissue. Sections of human cornea were immunostained with negative-control grade rabbit IgG, F(ab')(2) (the antigen recognition fragment of IgG yielded by pepsin digestion), and Fc fragments. Human corneal epithelium was homogenized in a buffer containing Triton X-100 and the water-insoluble residue was subjected to two-dimensional gel electrophoresis. Western blotting was performed on the gels to detect materials that bound with rabbit IgG Fc fragments. Spots in the gel that bound with the Fc fragments were collected and analysed by peptide mass fingerprinting (PMF). Using an antibody against a binding candidate, keratin 5 (suggested by PMF analysis), we checked the occurrence of this phenomenon. Immunohistochemistry showed that rabbit IgG bound to corneal epithelium via the Fc region but not F(ab')(2). Western blots using rabbit Fc fragments showed that some protein spots in the gel bound to the fragments. All of the binding materials were basic and had molecular weights of approximately 55 kDa. PMF analysis showed that the binding material was keratin 5; all binding materials on the transferred membrane were recognized by an anti-keratin 5 antibody. On corneal sections, anti-keratin 5 produced staining similar to that of rabbit IgG. These findings suggest that rabbit IgG binds to keratin 5 in the human corneal epithelium via the Fc region of the molecule.

Autoimmunity in the etiology of otitis media with effusion

Otitis media with effusion (OME) is one of the most common health problems seen in children. The role of autoimmunity in the etiology of OME has been discussed for a long time. The purpose of this investigation is to determine the role of circulating antibodies in the pathogenesis of OME. The presence of antibodies against rabbit tympanic bulla epithelium was investigated by indirect immunoflouresence in the serum samples of 25 patients with OME and serum samples of 25 healthy children as a control group. In the control group, positive staining was seen in only 1 case (4%), whereas 8 cases with OME were positively stained (%32). There was statistically significant difference between the 2 groups. The presence of antibodies against middle ear epithelium in the cases with OME suggest that autoimmunity might play a role in the formation of effusion in the tympanic cavity.

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.

Screening corneas for human immunodeficiency virus type 1 proviral DNA by polymerase chain reaction

PURPOSE

We evaluated the sensitivity of the polymerase chain reaction as a technique to directly screen potential donor corneas for human immunodeficiency virus type 1 (HIV-1) proviral DNA.

METHODS

DNA from the central 8.0-mm cornea, limbal cornea, aqueous humor, and retina from 22 eyes of 11 cadavers seropositive for HIV was extracted and amplified by polymerase chain reaction using primers specific for the gag and env regions of the HIV-1 genome. The identity of amplification products was confirmed by Southern blot hybridization.

RESULTS

Viral DNA was detected in four (18.2%) of 22 central corneas, one (4.5%) of 22 limbal corneas, one (6.3%) of 16 aqueous humor samples, and seven (31.8%) of 22 retinas. No correlation was noted between the presence of HIV-1 proviral DNA in samples from the central cornea and from the other tissues tested from the same eye.

CONCLUSIONS

Within the limits of our assay, processing and analysis of limbal cornea, aqueous humor, and retina by polymerase chain reaction may not reliably ascertain the presence of HIV-1 in the central, transplantable cornea.

Mapping of Fc gamma receptors in the human and porcine eye

By using an immunohistochemical technique, we detected a strong reaction product for Fc gamma receptors in the keratoconjunctival epithelium, uveal trabecular meshwork, optic nerve, and muscle walls of the retinal and ciliary vessels of infant human eyes; moderate staining was seen on the corneal endothelium, corneoscleral trabecular meshwork, non-pigmented ciliary epithelium, ciliary muscle fibers, endothelial lining of ocular blood vessels, as well as the anterior region of Muller cells, the outer nuclear layer, and pigment epithelium of the retina. In aged human and porcine eyes, the same structures stained somewhat less intensely than did those in infant human tissues. Primary cultures of porcine trabecular cells demonstrated a more intense immunoreaction product than did tertiary cultures. We discuss the possible role of Fc gamma receptors in various ocular inflammatory conditions and the implications of age-dependent expression by human trabecular cells in the pathogenesis of open-angle glaucoma.