BACKGROUNDGraves' ophthalmopathy/orbitopathy (GO) patients often suffer ocular surface damages and tear fluid proteins play a significant role in maintaining healthy ocular surfaces, while changes in tear protein components reflect the changes ocular surface abnormalities. In this study proteomics techniques were used to investigate tear protein compositions in GO patients.

METHODSWe carried out a case-control study by comparing tear fluid contents of GO patients with that of healthy subjects. In the first step the tears were subjected to SDS-PAGE electrophoresis and then single protein bands were analyzed by to in-gel trypsin digestion and nano-flow liquid mass spectrometry (LC-MS/MS) using a MS software.

RESULTSIn tear samples of GO subjects, the protein fractions of inflammation-related protein immunoglobulin kappa chain C region (IgKC) and serum albumin were essentially reduced, whereas a novel isoform of complement component 3 (C3), which we detected in control subjects, was completely absent in the GO patients' tears.

CONCLUSIONSReduced protein concentrations of particularly IgKC and complement C3 as well as albumin in the tears of GO patients may contribute to changes in their ocular surfaces via diminished reactive oxygen species (ROS) depletion and adaptive immune responses. The completely absent of C3 in the GO patients' tears, may imply that an important inflammatory signaling pathway is affected, which needs further investigation.