• This prospective study published in December in Clinical and Experimental Ophthalmology examined mannose-binding lectin (MBL) levels and function in inflamed and noninflamed eyes, and evaluated its relationship to blood mannose-binding lectin levels and function. The results demonstrate that MBL, which plays a central role in the innate immune response as a pattern recognition molecule that activates the complement cascade, is significantly elevated in inflamed human eyes but virtually undetectable in noninflamed eyes. The authors say this suggests that it plays a role in sight-threatening ocular inflammation.

    They collected paired blood and ocular samples (aqueous and/or vitreous) from 27 patients. Twelve of them had inflamed eyes, of whom 11 had proven or suspected endophthalmitis and one had herpetic retinal vasculitis. Fifteen patients with noninflamed eyes undergoing elective cataract surgery served as controls.

    The authors found that 10 patients (37 percent) were MBL-deficient, defined as having MBL levels less than 500 ng/mL. Blood MBL levels (P = 0.16) and C4 deposition function (P = 0.43) were not significantly different between controls and cases. As expected, there was a high correlation between blood MBL levels and function (r2 = 0.74). The level of MBL was significantly greater in inflamed eyes than noninflamed eyes (P < 0.01), as was C4 deposition function (P < 0.01).

    The authors say these results demonstrate that there are significantly higher amounts of this important innate immune system pattern recognition receptor in the eye when inflammation is present. They conclude that MBL is probably blood-derived and it is not yet established whether low levels contribute substantially to a local bactericidal immune response. They say that MBL requires more study, as alterations in its function may relate to intraocular infections, inflammation and AMD.