Immunohistochemical localization of endogenous placental HCII. Formalin-fixed sections were stained with hematoxylin and eosin (A) or immunostained with anti-HCII antibody (B) or nonimmune purified IgG (C). V indicates vessel; S, stroma; and T (arrowheads), syncytiotrophoblast layer. Original magnification, 400 ×.