Carolyn M. Kalsow

S-antigen: Characterization of a pathogenic epitope which mediates experimental autoimmune uveitis and pinealitis in Lewis rats

S-antigen (48K protein) is a photoreceptor cell protein highly pathogenic for the induction of experimental autoimmune uveitis (EAU) and intimately involved in the visual process. EAU is characterized, in part, as a T-cell mediated autoimmune disease which results in a severe inflammation of the uveal tract, and pineal gland. In order to determine specific sites in S-antigen responsible for its pathogenicity we synthesized twenty-three peptides, corresponding to the entire 404 amino acid sequence, and tested each peptide for its ability to induce EAU in Lewis rats. One peptide, peptide M (18 amino acids in length), was found to be highly pathogenic and consistently induced an EAU that was identical to the disease caused by native S-antigen. Clinically, the disease that developed in the eye was characterized by iris and pericorneal hyperemia, followed by inflammatory exudates in the anterior and vitreous chambers. Histopathologically a severe inflammatory response was observed which resulted in the complete destruction of the photoreceptor cell layer of the retina. In order to more fully characterize this pathogenic site, 14 additional smaller peptides (eight to eighteen amino acids in length) corresponding to the left and right portions of peptide M were synthesized. Of these peptides, peptide M16L, M15L, and M12L induced EAU, further localizing this pathogenic site to a small well-characterized region of S-antigen consisting of twelve amino acids. In addition, animals with ocular inflammatory disease had an associated pinealitis characterized by a lymphocytic infiltration of the subcapsular and central area of the pineal gland. The significance of these findings and the relationship of S-antigen in the pathogenesis of EAU and other autoimmune diseases is discussed.

Pinealitis accompanying equine recurrent uveitis.

There is no direct verification of pineal gland involvement in human uveitis. Specimens of pineal tissue are not available during active uveitis in human patients. Naturally occurring uveitis in horses gives us an opportunity to examine tissues during active ocular inflammation. We examined the pineal gland of a horse that was killed because it had become blind during an episode of uveitis. The clinical history and histopathology of the eyes were consistent with post-leptospiral equine recurrent uveitis. The pineal gland of this horse had significant inflammatory infiltration consisting mainly of lymphocytes with some eosinophils. This observation of pinealitis accompanying equine uveitis supports the animal models of experimental autoimmune uveoretinitis with associated pinealitis and suggests that the pineal gland may be involved in some human uveitides.

Effect of denaturization on the immunogenicity and uveitogenicity of retinal S-antigen

Previous studies have shown that alteration of pH or temperature of retina extract can affect its complement fixing reactivity with anti-S-antigen serum. To examine the effect of pH or heat on the immunogenicity and uveitogenicity of purified bovine S-antigen, guinea-pigs were injected with pH- or heat-treated S-antigen and evaluated for clinical and histopathological signs of uveoretinitis, histopathology of pineal gland, serum and intraocular S-antigen antibody reactivity, and S-antigen skin test reactivity. Guinea-pigs that received pH 7 or pH 10 treated S-antigen responded as did those that received untreated S-antigen. Guinea-pigs injected with pH 4 or heat-treated S-antigen exhibited lower incidence, later onset and less severe uveitis than those that received untreated S-antigen. Systemic responses of skin test reactivity to S-antigen were not different from those of the control group; pineal gland involvement and serum anti-S antibody reactivity were slightly reduced. Skin test responses of animals receiving treated antigen were less to the treated (injected) antigen than to untreated S-antigen. In addition, antibody responses of guinea-pigs receiving pH 4 or heat-treated antigen were less to the treated (injected) antigen than to untreated S-antigen. These results suggest that the sites on the S-antigen molecule responsible for various aspects of pathogenicity and immunogenicity do not have the same sensitivity to physical/chemical treatment and may reside on different parts of the molecule. Furthermore, the reactive sites especially for antibody and skin test reactivity, may be continuous sites.

Phlyctenular Keratoconjunctivitis Associated with Dolosigranulum pigrum

Phlyctenular keratoconjunctivitis is a nodular inflammation of perilimbal tissue that is probably a local immune-mediated response to a systemic sensitization. Although Mycobacterium tuberculosis and Staphylococcus aureus have been most frequently associated with phlyctenular eye disease, diverse microbes such as Chlamydia sp. and intestinal parasites such as Hymenolepsis nana 4 have also been implicated. Phlyctenules can also be seen in patients with blepharitis and ocular rosacea. In this report, we describe a case of bilateral phlyctenular keratoconjunctivitis associated with Dolosigranulum pigrum in a pediatric patient with asthma and environmental allergies. This newly recognized bacterial species has not been previously isolated in cases of phlyctenulosis. We discuss the pathogenesis of phlyctenular keratoconjunctivitis in our patient along with considerations for future diagnosis and management.

Response of guinea pigs to the synthetic peptide-M of the uveitogenic, retinal S-antigen: antisera immunofluorescent reactivity on normal guinea pig retina

S-antigen can elicit an experimental autoimmune uveitis (EAU) and pinealitis (EAP) in experimental animals. The sera of these animals have immunohistochemical reactivity with the photoreceptor cells of normal retina and pinealocytes. Lewis rats injected with the synthetic peptide-M corresponding to a specific sequence of S-antigen also develop an EAU and EAP. In this study we have investigated the immunohistochemical reactivity pattern of sera of guinea pigs injected with peptide-M. We found reactivity in the area of Mullers cells of normal guinea pig retina. Some of the sera showed weak reactivity with retina photoreceptors cells and pinealocytes. These patterns of reactivity are not seen in control sera of uninjected or saline in adjuvant injected guinea pigs. These results are consistent with observations of experimental and human uveitides.

Cellular Infiltrate in Rheumatoid Arthritis-associated Paracentral Corneal Ulceration.

ABSTRACT Purpose: To investigate an immunopathogenesis of central and paracentral corneal ulceration associated with rheumatoid arthritis. Methods: Sparse infiltrating cells in the ulcer area were identified by immunohistochemistry applied to archived formalin fixed, paraffin embedded tissues that had been recovered from patients undergoing penetrating keratoplasty necessitated by rheumatoid-associated central or paracentral corneal ulceration. Results: Clinically, the ulcers presented as non-infiltrated lesions with a modicum of other ocular inflammation. Sparse T-lymphocytes were consistently identified in the subepithelial areas adjacent to the ulcer, with some neutrophils and macrophages in the stroma. B-lymphocytes were not detected. MHC Class II antigens reactivity was noted on some infiltrating cells and on corneal endothelium of two specimens. Conclusions: Immunohistochemistry of archival tissue facilitated detection and identification of sparse infiltrate in this infrequent corneal melting. Selective, consistent finding of T-lymphocyte infiltration in the ulcer area supports an immunopathogenesis of this clinical entity.

Immunochemical evaluation of S-antigen of rabbit pineal gland

Purified S-antigen of photoreceptor cells induces experimental autoimmune uveoretinitis (EAU) and experimental autoimmune pinealitis (EAP) in laboratory animals. However, in rabbits, S-antigen induces only EAU without EAP. To evaluate this difference, the authors studied immunochemical reactivity of rabbit pineal gland with a panel of anti-S-antigen monoclonal antibodies (MAb). Rabbit pineal gland reacted with the MAbs by ELISA and immunoblot but not by immunohistochemistry. In contrast, rabbit retina like guinea pig retina, guinea pig pineal gland and bovine retina reacted with these MAbs by immunohistochemistry as well as by ELISA and immunoblot. Also, S-antigen purified from rabbit retina reacted as did bovine and guinea pig S-antigen. Therefore, S-antigen in situ in rabbit pineal gland is different from S-antigen of rabbit retina and different from S-antigen of pineal gland and retina of other species. Just as the MAbs did not react with S-antigen in rabbit pineal gland, it is possible that S-antigen activated lymphocytes may not recognize S-antigen in rabbit pineal gland and thereby not induce EAP.