COMPLEMENT AND COMPLEMENT REGULATORY PROTEINS IN HUMAN TEARS

Purpose. The complement system is part of the innate defense system of the body, and it contributes to inflammatory conditions. The current study examined tears for the presence of complement components, the ac tivity of the components, and the presence of regulatory components. M ethods. The significance of a functional complement system in tears Ma s examined in four ways. First, the presence and concentration of comp lement components in tear samples (open-eye, closed-eye, and reflex te ars) was examined by sandwich enzyme-linked immunosorbent assay. Secon d, the presence of an active pathway in each tear type was established by supplementation of complement-deficient sera. Third Western blotti ng of tear samples was used to determine whether complement components were activated in tears. Fourth, the presence of regulatory component s was examined by enzyme-linked immunosorbent assay and by the inhibit ion of the ability of tears to supplement deficient sera. Results. Com ponents Clq, C3, factor B, C4, C5, and C9 were detected in closed-eye tears. Only C3, factor B, and C4 were detected in open-eye and reflex tears. Tears were able to supplement complement-deficient sera, indica ting that the components were in an active state. Complement component s C3, factor B, C4, and C9 were activated in closed-eye tears. The reg ulatory protein decay-accelerating factor was found only in closed-eye tears. Lactoferrin, another regulatory protein present in all tear ty pes, Mas shown to inhibit complement-mediated red blood cell lysis, al though the inhibition by closed-eye tear lactoferrin was reduced compa red to that isolated from other tear types. Conclusions. This study ha s demonstrated that the complement system in tears was functionally ac tive and that the concentration of all components was increased greatl y in closed-eye tears. In spite of the presence of regulatory proteins , proteins of the complement cascade in tears were shown to be activat ed.