Defects in the physical integrity of the villous membrane; Their origin and possible significance

DEFECTS IN THE PHYSICAL INTEGRlTY OF THE VILLOUS MEMBRANE; THEIR ORIGIN AND POSSIBLE SIGNIFICANCE. G J Burton and J N Skepper. Department of Anatomy, University of Cambridge, Cambridge CB2 3DY. U.K. The physical integrity of the syncytiotrophoblast must clearly play a crucial role in limiting both the transplacental spread of infection and maternal hnrnune attack upon the fetus. It is known, however. that during pregnancy maternal sensitization to fetal HLA antigens can occur, and this along with evidence of fetal sensitization to maternal lymphocytes has been taken to be indicative of physical defects in this barrier. The sites and camx of these defects have never been identified. however. Using scanning microscopy we have observed circumscribed areas of syncytial damage in material from both early and late gestation. The majority of these are circular in outline with a diameter of lo-20 pm. which leads us to believe they result from the disruption of sites of villous apposition and syncytial fusion. The identification by correlative transmission electron microscopy of both maternal lymphocytes attached to these areas and the deposition of fibrin. confirms that these lesions do occur in vivo. By breaching the syncytiotrophoblastic apical membrane these lesions may provide access for infectious agents to the deeper layers of the trophoblast. or even to the stromal villous core with its contained Hofbauer cells. They may also allow the initiation of localised immune attacks against exposed fetal cells bearing HLA antigens. Morphological appearances suggest these areas may progress to sites of frank fibrinoid necrosis,

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