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2009 OMIG, Abstract 20

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Mannose Binding Lectin as part of the Complement System: Absent in the Normal Eye but Present in the Inflamed Human Eye.
S. Chow1, M. Daniell1, M. Dean3, J. Depla4, D. Eisen2
1Department of Ophthalmology, Royal Melbourne Hospital, Melbourne Australia,  
2Infectious Diseases Service, Royal Melbourne Hospital, Melbourne, Australia,
Co-operative Research Centre for Vaccine Technology, Brisbane, Australia,
Vitreo-retinal Unit, Royal Victorian Eye and Ear Hospital, Melbourne Australia. 

Purpose: Mannose Binding Lectin (MBL) plays a central effector role in the lectin pathway of complement activation. frequently occurring MBL genetic polymorphisms result in MBL deficiency, which has been shown to increase susceptibility to infection. We characterized MBL levels and function in normal and inflamed human eyes, and evaluated its relationship to serum MBL level and function.
Methods: Blood and ocular samples (aqueous and/or vitreous) were collected from 29 patients. 15 control samples were obtained during elective cataract surgery. 14 inflamed samples were obtained from patients with endophthalmitis (11), herpetic retinal vasculitis (1) and macula-off retinal detachments (2). MBL levels and function were quantified with ELISA mannan binding and C4 deposition assays respectively.
Results: Ten patients (34.5%) had low serum MBL levels (<500ng/ml). There was no difference in the serum MBL levels or function of patients with normal or inflamed eyes. There was a high correlation between serum MBL levels and its function (r2=0.769). There was significantly more MBL in the aqueous of inflamed eyes than normal eyes measured as level (p=0.0002) or function (p=0.0013), and no difference in MBL levels of aqueous and vitreous in inflamed eyes. However, the correlation between ocular MBL level and its complement activation function was substantially lower than expected in the inflamed eye, suggesting local inhibition of its function.
Conclusion: As with the classical pathway, the lectin complement pathway is present in the eye but is persistently modulated to restrict the extent of sight-threatening inflammatory reaction. In our study, MBL is present only in inflamed eyes, and its complement activation function appears inhibited when it is present.
Disclosure Code: N

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