Abstract
Abstract: :
Purpose: Transplantation studies indicate that the uvea is immune privileged. Here we investigate whether there is a relationship between CGRP nerve terminals and antigen presenting (AP)-cells in the mouse uvea. Methods: 65 Balb-c mice of different age groups (1 day - 13 months) were investigated. Antigen presenting cells were visualized by a monoclonal F4/80 antibody, CGRP nerve fibers and terminals by a polyclonal anti rabbit CGRP antibody. For double staining whole mount preparations of the iris and ciliary body fixed in Zamboni fixative over night were incubated with the F4/80 antibody for 12h and subsequently with CGRP antibodies for the same time. As secondary antibodies streptavidin Cy2 and Cy3 were used. For immunocytochemical demonstration of the CGRP-terminals the whole mounts were prepared in a similar way as for light microscopy but incubated with anti-rabbit ultrasmall gold as secondary antibody. The specimens were then embedded in Epon and serial sections through the iris were analysed. Results: At day 1 a pupillary membrane was still present. Single large round cells entered the anterior surface of the iris stroma via the capillaries of the pupillary membrane. There were no other stained cells in the iris and ciliary body. CGRP positive nerve fibers and terminals were not in contact with the cells but were found throughout the entire iris up to the capillaries of the pupillary membrane. At day 4 the number of stained cells increased significantly and in addition to round cells there were star-like cells in the iris- and ciliary body-stroma. The CGRP terminals were no longer present at the pupillary rim, but were more numerous at the iris root up to the upper 2/3 of the iris. At day 7, in addition to numerous cells in the iris stroma, single cells also appeared in the epithelium of the iris/ciliary body. At that time some of the large round F4/80 stained cells at the iris root were surrounded by CGRP nerve terminals. In older eyes, the number of stained cells in the epithelial layer and in the iris stroma increased, but the amount showed individual variations. The number of large cells surrounded by CGRP terminals increased with age especially in the aqueous humor outflow region. Conclusions: Our results demonstrate for the first time 1. that AP-cells can enter the iris via the pupillary membrane and 2. that there are CGRP innervated AP-cells in the mouse uvea. It is tempting to speculate that the innervation of the AP-cells might play a role for the immune privilege of the uvea.
Keywords: immunohistochemistry • anatomy • anterior segment