Class II histocompatibility antigen expression by cellular components of vitreous and subretinal fluid in proliferative vitreoretinopathy

Proliferative vitreoretinopathy (PVR) is the major cause of failure in retinal detachment surgery. It is characterized by the formation of membranes extending along both surfaces of the detached retina and within the vitreous, but the nature of the growing cells has not yet been determined. Using cytologic and immunocytologic procedures with 13 different monoclonal antibodies directed against Class II histocompatibility antigens and various markers of epithelial and immunocompetent cells, 30 specimens were studied of vitreous or subretinal fluid removed from patients with PVR. Five main types of cells could be identified: heavily pigmented cells, poorly pigmented ones, large totally unpigmented macrophage-resembling ones, smaller unpigmented cells, and lymphocytes. Analysis of intravitreal pigment granules, using autofluorescence by epiillumination and cytologic procedures, showed two different populations of pigmented cells: one with autofluorescent lipofuscin granules and the other with exclusively melanin pigment. Immunostaining procedures confirmed the epithelial nonmacrophage lineage of the intravitreal and subretinal cells because most of these cells were positive for cytokeratin but negative for macrophage markers. In addition, 40-100% of these epithelial-derived cells strongly expressed Class II histocompatibility antigens HLA-DR and -DQ. Lymphocytes were found in 13 specimens; B-cells were seen, but no T-lymphocytes could be identified. These results confirm the involvement of retinal pigment epithelial cells and the strong morphologic changes they undergo during the course of PVR. Moreover, the expression of Class II histocompatibility antigens by the growing cells may be related to inflammatory phenomena, but their eventual role in the development and the extension of periretinal proliferation has not been determined.