IMMUNOHISTOCHEMICAL LOCALIZATION OF EXTRACELLULAR-MATRIX IN PERIVILLOUS FIBRINOID OF NORMAL HUMAN TERM PLACENTA

The extracellular matrix of perivillous fibrinoid in normal human term placenta was investigated by means of the indirect immunofluorescent technique. Polyclonal antibodies to collagen types I, III, IV, V, fibr onectin, fibrinogen, laminin, entactin and heparan sulphate proteoglyc an and monoclonal antibodies BC-1, IST-9 and IST-4 to human fibronecti n were used. The antigens can be grouped according to their presence i n fibrinoid as abundant (fibrinogen, fibronectin, heparan sulphate pro teoglycan, basement membrane collagen types IV and V), absent (laminin ) and variable between fibrinoids (interstitial collagen types I and I II, entactin). Our results also demonstrate that fibronectin in fibrin oid originates from placental cells (presumably cytotrophoblast). Mono clonal antibodies BC-1 and IST-9 specific to tissue fibronectin do not stain neighbouring placental extracellular matrix but do bind to fibr inoids on the same sections. Work by other authors has presented evide nce that fibrin actually originates from maternal blood and even makes an attempt to substitute the term ''fibrinoid'' for ''fibrin depositi on''. Our data on the composition of perivillous fibrinoids and the ab undance of extracellular matrix components do not support this view an d suggest that fibrinoid is a more relevant term for this interesting phenomenon, which deserves further investigation.