In vivo and in vitro deposition of immunoglobulin aggregates in the mouse eye

The possible role of specific mechanisms involved in the adherence process of immune aggregates to tissue components of the mouse eye was investigated in an experimental animal model. Passive intravenous administration of immunoglobulin aggregates to mice, resulted in the localisation of these aggregates in various organs, including the eye. In the eye a strong localisation was seen in the episcleral capillary plexus, whereas only a weak deposition was seen in the iris, ciliary body and choroid. No deposits were seen in the retina. To investigate the role of specific receptors for immune complexes in the eye, in vitro experiments were performed, whereby immunoglobulin aggregates were layered on cryostat sections of the mouse eye. These in vitro studies also showed an adherence of immune aggregates to the episcleral capillary region, but furthermore a deposition on mast cells scattered throughout the extra-ocular muscles. The in vitro binding of immunoglobulin aggregates to the episcleral capillary plexus could be inhibited by high concentrations of Fc fragments and monomeric IgG, but not with Fab fragments or 0.5 M NaCl. The in vitro adherence of aggregates to mast cells could not be blocked by the inhibitors employed in our study and could therefore be distinguished from the interaction of aggregates with the episcleral capillary plexus. These results indicate that the ocular deposition of immunoglobulin aggregates in the episcleral capillary plexus of the mouse eye is (immune) specific and mediated by Fc receptors.