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was investigated by immunohistology of frozen sections, and by flow cytometry of decidual cell dispersions.

The ~7.5 IL-2 receptor (IL-2R) was expressed on decidual cells identified by double labelling in flow cytometry as CD56-positive large granular lymphocites (LGL). No expression of the ~5.5 (CD25) IL-2R was detected. The IL-4R protein was expressed on some decidual LGL, most macrophages and T cells, and on the basal face of the glandular epithelium.

Incubation of flow cytometrically purified CD56-positive LGL with IL-2 failed to induce the ~55 IL-2R qr to increase the expression of the ~75 IL-2R or the IL-4R. Decidual LAGI proliferated in response to IL-2, and IL-4 inhibited this proliferation.

The results show that decidual cells have the potential to respond to IL-2 and IL-4, and suggests a role for IL-4 in locally suppressing the maternal immune response in early pregnancy.

EFFECT OF DIFERRIC TRANSFERRIN AND CULTURE TIME ON TRANSFERRIN-RECEPTOR NUMBER AND DISTRIBUTION IN SYNCYTIOTROPHOBLAST IN VITRO J. Starreveld, M. J. Kroos, H. G. v. Eijk &J. P. v. Dijk (Chemical Pathology, Erasmus University Rotterdam, PO Box 1738,300O DR Rotterdam, The Netherlands)

In vivo cytotrophoblast lacks transferrin receptors (TfRs). After isolation from term placenta’s these cells can be cultured in vitro. In vitro cytotrophoblast cells differentiate to syncytiotrophoblast, form a syncytium and express TfRs.

Expression of TfRs is time dependent and transport of iron to the fetus is regulated by variation of the number of cell-surface bound TfRs. If human diferric transferrin (hTf) is added to the culture medium TfR expression is reduced. In this study the influence of culture time combined with hTf on the total number and the surface-expression of Tflis was investigated. It appeared that TfR expression increases during in vitro culture. Cells cultured in a medium supplemented with hTf reduce the number of TfRs on the cell surface in comparison to cells cultured in an iron-free medium. However, cells cultured in an hTf- containing medium continue to increase the number of cell-surface related TfRs at a rate highly comparable to that of cells cultured in an iron-free medium. Total number of TfRs increases during culture. TfR expression is clearly influenced by a differentiation process as well as a (iron transport) regulation mechanism. These processes may interfere and in this way influence the experimental results. Other in viuro experiments concerning trophoblast function might be influenced by this interference as well.

NUCLEOTIDE METABOLISM OF THE DECIDUA IN THE RAT PLACENTA I. H. Straatsburg & R. Gossrau (Department of Anatomy, Free University of Berlin, Ktinigin-Luise-StraBe 15, W-1000 Berlin 33, FRG)

There is biochemical evidence that nucleotides and the ectonucleotidases adenosine triphosphatase (ATPase), diphosphatase (ADPase) and monophosphatase (AMPase,