Immunopathologic study of the implantation site in molar pregnancy.

The implantation sites of 11 molar pregnancies were examined for the deposition of immunoglobulin and complemented by direct immunofluorescence. None of the 10 women experiencing their first molar pregnancy had immunoglobulin or complement deposition in the implantation site. The one patient with immunoglobulin and complement deposition in the implantation site was aslo the only patient experiencing a second molar pregnancy. Immunofluorescent staining for IgG, IgM, and C3 was confirmed to the decidual arteries in this patient and was unassociated with endovascular trophoblastic deposits. While only one of the 10 women with their first molar pregnancy had focal vasculitis at the implantation site, the patient with her second consecutive mole had diffuse vasculitis. Because molar implantation sites are generally free of immunoglobulin and complement deposition, molar pregnancies do not appear to induce a vigorous host humoral immune response at the time of presentation at the molar implantation site.