Rat CNS in experimental chronic serum sickness: integrity of the zonulae occludentes of the choroid plexus epithelium and brain endothelium in experimental chronic serum sickness.

The present study is an extensive systematic immunofluorescence and labelled electron microscopic investigation of chronic rat serum sickness brains. It is specifically directed at discerning effects of chronic serum sickness upon the zonulae occludentes of both the choroid plexus epithelium and the intra-cerebral endothelium. Although the choroid plexus is a known site of complex entrapment in systemic immune complex disorders, comprehensive immune studies of the CNS parenchymal vasculature have not yet been reported in either experimental or spontaneous immune complex disease. We examined by direct immunofluorescence techniques over 70 blocks of experimental chronic serum sickness brains taken from 16 animals with severe glomerular disease and found them to be uniformly negative for the presence of immune deposits. No horseradish peroxidase was seen beyond the restricting zonulae occludentes of either the choroid plexus or the cerebral endothelium in tissue from three serious affected animals. These structural barriers retained their integrity despite the extensive circulation and deposition of complexes and complement induced in the experimental model and the associated release of vasoactive substances.