Immunohistochemical proof of origin of macrophages in laser photocoagulation lesion in the retina.

The origin of the macrophages which appear in the subretinal space after laser photocoagulation on the rat retina was investigated using immunohistochemistry. The majority of macrophages located in laser lesions were found to be positive to staining for the specific rat monocyte/macrophage marker (ED1). The number of macrophages and activated macrophages were abundant after intense laser photocoagulation in which choroidal neovascularization was induced. After the retinal pigment epithelium (RPE) was damaged by intravenous administration of sodium iodate, the number of migrating macrophages in the subretinal space of lasered areas significantly decreased to a level comparable to the level found in control animals. These results suggested that the macrophages were derived mainly from monocytes in the blood, not from RPE cells, and that they may play a role in the development of the choroidal neovascularization.