Immunohistochemical analysis of human orbital tissue in Graves' orbitopathy.

PURPOSE: Immunohistochemistry of orbital tissues offers a correlation between the microscopic changes and macroscopic clinical manifestation of Graves' orbitopathy (GO). Summarizing the participation of different molecules will help us to understand the pathogenesis of GO.
METHODS: The pertinent and current literature on immunohistochemistry of human orbital tissue in GO was reviewed using the NCBI PubMed database.
RESULTS: 33 articles comprising over 700 orbital tissue samples were included in this review. The earliest findings included the demonstration of HLA-DR and T cell (to a lesser extent B cell) markers in GO orbital tissues. Subsequent investigators further contributed by characterizing cellular infiltration, confirming the presence of HLA-DR and TSHR, as well as revealing the participation of cytokines, growth factors, adhesion molecules and miscellaneous substances. HLA-DR and TSHR are over-expressed in orbital tissues of GO patients. The inflammatory infiltration mainly comprises CD4 + T cells and macrophages. Cytokine profile suggests the importance of Th1 (especially in early active phase) and Th17 immunity in the pathogenesis of GO. Upregulation of proinflammatory/profibrotic cytokines, adhesion molecules and growth factors finally culminate in activation of orbital fibroblasts and perpetuation of orbital inflammation. The molecular status of selected parameters correlates with the clinical presentation of GO.
CONCLUSION: Further investigation is warranted to define precisely the role of different molecules and ongoing search for new players yet to be discovered is also important. Unfolding the molecular mechanisms behind GO will hopefully provide insights into the development of novel therapeutic strategies and optimize our clinical management of the disease.