Investigation of the expression of amnion antigens by spiral arteries in human utero-placental tissues.

Two monoclonal antibodies raised against human amnion, GB3 and GB5, were used in an indirect immunoperoxidase method to investigate the expression of amnion antigens by spiral arteries in pregnant and nonpregnant uterine tissues. GB3 showed focal reactivity with occasional spiral arteries in the placental bed throughout pregnancy, but no GB3-staining was observed in nonpregnant endometrium. In contrast, GB5 showed bandlike circumferential reactivity with spiral arteries at all gestational ages examined. GB5-positivity showed no relation to the presence of endovascular or perivascular trophoblast. In nonpregnant endometrium, GB5 labeled rare spiral arteries. However, in a premenstrual specimen showing pseudodecidual change, there was circumferential reactivity with GB5 resembling that in pregnancy. The reaction patterns of GB3 or GB5 were not similar to those for two other basement-membrane components, fibronectin and type IV collagen. The results suggest that expression of the GB5 antigen may in part be regulated by hormones.