Immunoregulatory mechanisms in pregnancy. 1. Evidence for the alpha-fetoprotein-induced generation of suppressor cells in vitro.

The generation of active suppressor cells has been induced in vitro by preculturing of splenocytes from normal mice in the presence of mouse amniotic fluid (MAF) and alpha-fetoprotein (AFP). By using freshly explanted splenocytes, addition of such precultured lymphocytes abrogated the generation of specific cytotoxic lymphocytes (CTL) in primary mixed lymphocyte cultures. Effective suppression can be induced only when the precultured cells are added within the first 48 hr of culture. These suppressor cells are nylon-wool nonadherent and their effect could be almost abolished by treatment with anti-Thy-1,2 serum plus complement. The precursors of the suppressor cells are sensitive to hydrocortisone and resistant to low doses of radiation. The induction of suppressor cells by AFP may be one of the mechanisms resulting in deviant immune response during pregnancy and in the newborn.