Membrane Fluidity of Trophoblast Cells and Susceptibility to Natural Cytotoxicity

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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.