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C. E. Thirkill; Microbial-Induced Retinal Hypersensitivity (MIRH). Invest. Ophthalmol. Vis. Sci. 2007;48(13):5191.
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The clinical significance of immunologic reactions within the eye is increased if it includes known autoantigens, or is focused upon a single cell population. Commonly the cause remains unknown. The possibility of chronic microbial infection was investigated upon encountering a case of Sjogren's syndrome accompanied by a non-inflammatory retinopathy in a patient with a history of chronic urinary tract infection. A bacterium with the characteristics of Escherichia coli was isolated from a urine sample provided by the patient, and evaluated for evidence of any antigenic relationship with retina. An 'E.coli' protein approximating 50 kd was found to react with rabbit anti-retina serum, and the patient's serum, prompting the search for the retina cell-type involved, and any similar immunologic activity in patients with various forms of idiopathic retinopathy.
Archived serums from 15 patients with retinopathies of unknown cause were evaluated for abnormal immunologic activity upon Western blots of extracts of whole pig retina, and the 'E.coli'. The retinal cells expressing the 50 kd antigen were identified by immuno-histochemistry on sections of monkey retina.
Six of the 15 patients were producing antibodies reactive with the 50 kd 'retina-reactive E.coli protein'. Patient's antibodies affinity purified from this region of the blot relocated to a 50 kd region of a Western blot of whole retina, and the ganglion cell layer of monkey retina
The implication of microbes in the sensitization process of a growing number of autoimmune diseases has increased in recent years. Microbes involved in chronic infections often incite an appreciable immunologic response. Any cross-reactive component shared between the agent and host tissues might result in organ-specific autoimmune reactions detrimental to the optimal function of the organ involved. This identification of a bacterial antigen sharing immunologic characteristics with retina expands upon previous findings of others who have demonstrated similar evidence implicating an immunologic relationship between some microorganisms and specific ocular tissues. In this case, a bacterium isolated from an individual with Sjogren's syndrome, a recognized autoimmune disease, complicated here by a chronic urinary tract infection, represents an additional example of the process. The 50 kd 'E.coli' protein is to be isolated and characterized further to identify its amino acid sequence(s) to permit comparisons with those of recognized retinal antigens, and any autoantigenic characteristics demonstrable in laboratory animals that might identify the 'coli-connection' as a preventable form of immune-mediated vision loss.
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