Immunosuppression by conditioned media derived from a cloned choriocarcinoma cell line in serum-supplemented and defined media.
OBJECTIVE
Immunosuppressive factor(s) of trophoblast origin may contribute to the immunological privilege afforded the fetal allograft. Characterization of these immunoregulators in humans has been impeded by a lack of sufficient quantities of early gestational trophoblast for experimentation.


METHODS
In this study, a cloned choriocarcinoma cell line (BeWo) was evaluated as an experimental model of trophoblast-derived immunoregulation. BeWo cells were cultured in both serum-supplemented (15% fetal bovine serum; FCS-CM) and serum-free (10% bovine serum albumin, BSA-CM; 0.01% gelatin, Gel-CM) media. Immunosuppressive activity was determined through the use of interleukin-2-dependent (CTLL-2) and -independent (LBRM) cell lines. Human chorionic gonadotropin (hCG) levels were determined by an immunoradiometric assay, and cellular morphology was assessed by light microscopy.


RESULTS
In the serum-supplemented cultures, a portion of cells underwent transformation from single nucleated cytotrophoblast to multinucleated syncytiotrophoblast during days 1 to 5 of culture and was accompanied by a rise in hCG. Serum-free cultures were characterized as islands of cytotrophoblast and did not exhibit differentiation. FCS-CM suppressed CTLL-2 and LBRM proliferation with estimated EC50 values of 415 and 280 micrograms protein/mL, respectively. Gel-CM suppressed CTLL-2 and LBRM proliferation with EC50 values of 12 and 7 micrograms protein/mL, respectively. BSA-CM suppressed CTLL-2 proliferation with an EC50 of 132 micrograms protein/mL, but failed to suppress LBRM proliferation below 50% of control.


CONCLUSIONS
These results suggest that the BeWo cell line is a promising model for the study of trophoblast-derived suppressive factors and that these factors can be generated in serum-free medium.
Bennett
W A
WA
Department of Obstetrics and Gynecology, University of Mississippi Medical Center, Jackson 39216-4505, USA.
Brackin
M N
MN
Long
C A
CA
Cowan
B D
BD
D000818:Animals; D001685:Biological Factors / Q000378:metabolism* / Q000494:pharmacology; D002417:Cattle; D002459:Cell Fusion; D002822:Choriocarcinoma / Q000378:metabolism* / Q000473:pathology; D006063:Chorionic Gonadotropin / Q000032:analysis; D002999:Clone Cells; D003470:Culture Media / Q000494:pharmacology*; D017077:Culture Media, Conditioned / Q000494:pharmacology*; D016895:Culture Media, Serum-Free / Q000494:pharmacology*; D005260:Female; D005312:Fetal Blood; D006801:Humans; D007108:Immune Tolerance / Q000187:drug effects*; D007376:Interleukin-2 / Q000494:pharmacology; D008213:Lymphocyte Activation / Q000187:drug effects*; D013601:T-Lymphocytes / Q000187:drug effects*; D014327:Trophoblasts / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D014594:Uterine Neoplasms / Q000378:metabolism* / Q000473:pathology
D001685:Biological Factors; D006063:Chorionic Gonadotropin; D003470:Culture Media; D017077:Culture Media, Conditioned; D016895:Culture Media, Serum-Free; D007376:Interleukin-2