(A) Epithelium (e) of the umbilical cord is simple columnar with microvilli (mv). A distinct connective tissue stroma (ct) separates the epithelium from channels within the cord viz, umbilical artery, umbilical vein and ductus vitellointestinalis. Haematoxylin and eosin. (B) Immunohistochemistry of the uteroplacental complex for IL-1 α shows the uterus (ut) and the ectodermal portion of the placenta (ec) to be modestly positive. Leucocytes (leu) of both uterus and placenta and yolk sac endoderm (en) are positive. Egg envelope (ee). (C) Immunohistochemistry of paraplacental cells for IL-1 α shows the epithelial cells (e) apices to be positive but the mucous (m) component is negative. (D) Immunohistochemistry of the umbilical cord for IL-1 α reveals cytoplasmic vesicles in umbilical cord epithelium (e) are positive and microvilli (mv) are negative.