Abstract
Purpose:
To describe the distribution of CD163+ and CD68+ cells, markers of M1 and M2 macrophages and microglia, in the normal adult human eye in order to test the hypothesis that intraocular immune competent cells are TH2/M2 polarised.
Methods:
Six eyes (4 donors, aged 52-59 years) from the NSW Lions Eye Bank, with corneas removed for transplantation, were processed for routine H&E and histological examination. Eyes had no history of ocular disease and were normal on macroscopic examination. Sections were stained with anti-human CD163 (clone 10D6) and anti-human CD68 (clone 514H12) using the proprietary Bond Polymer Red Detection kit from Leica (Catalogue No DS 9390). Nuclei were counterstained with haematoxylin. CD163 and CD68 staining was assessed in all compartments of the globe (except cornea).
Results:
CD163+ macrophages were abundantly distributed throughout the choroid while CD68+ macrophages were clustered in the outer choroid. In one eye, CD163+ choroidal macrophages were seen beneath small hard drusen and beneath an anteriorly migrated hypertrophied retinal pigment epithelial cell. Within the retina, CD163+ microglia were infrequently seen in the inner retina around retinal vessels, within the ganglion cell layer, abutting the internal limiting membrane, within Henle's fibre layer and very occasionally in the inner nuclear layer. CD163+ cells with plump epithelioid morphology were seen in the subretinal space of the peripheral retina near the ora serrata. CD68+ cells were entirely absent in the neural retina. CD163+ macrophages were also frequently seen within ciliary body stroma and anterior iris stroma, between fibres of the optic nerve, and within conjunctival epithelium and stroma. CD68+ cells were absent from these sites.
Conclusions:
Excepting the outer choroid, intraocular microglia and macrophages in this series of normal human eyes expressed CD163 and not CD68, supporting the idea that the normal intraocular immune environment is TH2/M2 polarised.
Keywords: 557 inflammation •
555 immunomodulation/immunoregulation •
638 pathology: human