Immunohistochemistry study of the glaucomatous and normal human trabecular meshwork

Although class II-expressing cells have been reported previously in the human trabecular meshwork (HTM), the exact identity of these cells and their possible role in the normal and the pathological state remains unclear. Preliminary results suggest increased human leucocyte antigen (HLA)-DR expression in the glaucomatous TM. To investigate this possibility, 20 trabeculectomy specimens obtained from patients with primary open-angle glaucoma (POAG) were examined immunohistochemically for HLA-DR, leucocyte common antigen (LCA; CD45) and a macrophage marker (CD68). The patients varied in age from 42 to 86 years (average, 69 years). The degree of antibody staining in the TM was compared with that of 20 human control eyes obtained from an eye bank less than 24 h after death. The donors varied in age from 47 to 91 years (average, 69 years); there was no known history of eye disease amongst the control group. Evaluation of specimen was performed by two observers using a grading system ranging from negative (0) to strongly positive (3) and by computer-aided optic densitometry. HLA-DR-positive cells were present in both the normal and the glaucomatous TM. Occasional cells stained for LCA and CD68 in the TM of both groups. Subpopulations of the HLA-DR-staining cells were apparent on serial sectioning. An age effect on antigen staining was not observed; postmortem delay of greater than 48 h resulted in decreased specimen antigenicity. Both evaluation techniques failed to reveal a significant difference in HLA-DR, LCA or CD68 staining between the glaucomatous and the normal TM.