A peripheral venous blood sample was collected from each patient, centrifuged at 700× g for 10 minutes, and serum aliquots were stored at −80°C until examination.
Swine eyes from healthy animals (aged 3–6 months) were enucleated, immediately frozen in liquid nitrogen, and embedded in optimum cutting temperature compound. Cryostat sections (7 μm) were mounted on poly-L-lysin–coated slides, and stored at −20°C until usage. Tissue sections were dried at room temperature (RT) for 30 minutes, and fixed in acetone. Unspecific binding sites were blocked by incubating slides for 20 minutes with 5% rabbit serum, 1% bovine serum albumin, and 1% Fc-blocking reagent (Miltenyi Biotec; Bergisch-Gladbach, Germany) in PBS with 1% fetal calf serum (FCS). After incubation with patient's or control's serum at 1:100 or 1:200 in PBS or PBS as a negative control in a moist chamber for 30 minutes, the sections were washed with PBS/1% FCS, incubated with H2O2 3% for 5 minutes, washed again, and were incubated with horseradish peroxidase (HRP)–conjugated rabbit-anti-human-IgG-antibody (Dako Germany, Hamburg, Germany) diluted 1:100 in PBS/1% FCS with 5% swine serum for 20 minutes. After washing, slides were incubated for 15 minutes with 3-amino-9-ethylcarbazol diluted in acetate buffer, previously activated with H2O2, fixed with acetate buffer and 4% formaldehyde for 10 minutes, and rinsed in acetic acid (1%). Nuclei were stained with hematoxilin solution, Gill No. 3 (Sigma-Aldrich, Taufkirchen, Germany). Finally, tissue sections were embedded in Aquatex (Merck, Darmstadt, Germany), covered with cover slides, and dried at RT.
Presence of positive staining on the eye sections was analyzed independently by two observers in masked fashion. Staining patterns were classified as nuclear or nonnuclear. No quantification of tissue staining was attempted.