Proteomic patterns in SS patients with dry eye syndrome have identified proteins involved in host defense, immune response, inflammation, and apoptosis, including a-2-HS-glycoprotein, coagulation factor II, transferrin, orosomucoid, apolipoprotein A-II, elastase 2, serpin peptidase inhibitor, clusterin, keratin 1, C3, and 4A. Here, C3 is linked to dry eye syndrome.