• Membrane lipid microviscosity;
  • lymphocytes;
  • cholesteryl hemisuccinate;
  • progesterone;
  • spontaneous abortion;
  • pregnancy

ABSTRACT: This study examines the relationship between membrane lipid microviscosity and susceptibility of villous trophoblast to lysis by natural cytotoxic cells.

Trophoblast-enriched cell suspensions prepared from term human placentae were treated with cholesteryl hemisuccinate (CHS)—a modulator of membrane lipid microviscosity. CHS-treated cells were more susceptible targets for natural lymphocyte cytotoxicity than were untreated controls. In binding experiments, increased binding of lymphocytes to CHS-treated target cells was found. Preincubation with progesterone prevented membrane rigidification by CHS. Progesterone, Cortisol, and estriol restored the impaired resistance of CHS-treated trophoblast cells to lysis.

We determined microviscosity and progesterone concentration in villous surface membranes, prepared from placentae from idiopathic spontaneous abortions and normal first-trimester pregnancies.

An inverse relationship was found between progesterone content and microviscosity of the membranes. Microviscosity of the membranes from abortion placentae was significantly higher (P < .01) and progesterone concentration was significantly lower (P < .001) than those in the membranes of normal first trimester placentae.