Brain capillary endothelial cells in vitro lack surface IgG Fc receptors

A reliable technique to produce consistently pure cultures of endothelial cells prepared from isolated rat brain capillaries has been established. The cells express many of the morphological and antigenic characteristics of endothelium in vivo, including the formation of tight junctions and possession of Factor VIII/von Willebrand Factor antigen (FVIII/vWF) and angiotensin converting enzyme (ACE). Using indirect immunofluorescence, surface IgG Fc receptors (FcR) could not be demonstrated, either when the cells were incubated in aggregated IgG, or in adult rat serum. Rat peritoneal macrophages served as a positive control. However, permeabilization of the endothelial cells with glacial acetic acid/ethanol prior to incubation with IgG allowed the demonstration of internal binding sites. The lack of surface receptors in the normal state does not rule out the possibility of their induction during pathological conditions.