Purpose: The aim of this study was to analyze lymphocyte infiltration using immunohistochemistry in proliferative diabetic retinopathy (PDR) membranes.
Methods: Sixteen patients, 13 with PDR and 3 without diabetes, underwent pars plana vitrectomy, and the epiretinal membrane was peeled. Formalin-fixed, paraffin-embedded epiretinal membrane tissues were processed for immunohistochemistry with anti-leukocyte common antigen (LCA), CD3, and CD20 antibodies. Lymphocyte density was determined by direct counting at a high magnification under a light microscope, which was compared with the patients' visual prognoses.
Results: The lymphocyte density ranged from 1 to 52 (mean, 9.5) in high-power fields. Of 13 membranes, 5 showed a lymphocyte density of >5 cells, whereas the other 8 membranes showed a cell number of <2. The former type is defined as a lymphocyte-rich epiretinal membrane (LERM). Infiltrated lymphocytes were immunohistochemically positive for CD3, a T-cell marker, but not for CD20, a B-cell marker. All patients with LERM had poor visual prognosis after vitrectomy. In contrast, the visual prognosis in 7 patients with non-LERM improved or remained unchanged. A significant association was observed between high-level lymphocyte infiltration in the epiretinal membrane and poor visual prognosis (P < 0.001). LCA(+) mononuclear cells were not observed in epiretinal membranes in the absence of diabetes.
Conclusions: These results suggest that the high-level infiltration of T lymphocytes into the PDR membrane is well correlated with poor visual prognosis. Histopathologic observation of the epiretinal membrane in patients with PDR may provide significant prognostic information.