Immunological studies of human placentae. Binding of complexed immunoglobulin by stromal endothelial cells.

Endothelial cells of foetal stem vessels in cryostat sections of normal, full-term human placentae bind fluorescein-conjugated heat-aggregated human IgG. Soluble immune complexes of sheep anti-human albumin also bind in a pattern that is similar to that of aggregated human IgG, but native human IgG is not bound by placental endothelial cells. Aggregated IgG binding, unlike soluble immune complexes, is blocked by pretreatment of the sections with antiserum to human IgM. Cross-blocking experiments with aggregated IgG and immune complexes suggest that they may be bound by different receptors.