Suppression of cellular immune responses by mouse amniotic fluid

Mouse amniotic fluid (AF) strongly inhibited the in vitro generation of cell mediated cytolytic responses to allogeneic EL4 tumor cells. Potent immunoregulatory capabilities of AF in utero are suggested by in vitro suppression of immune responses by concentrations below physiological levels and by the inhibition of lytic function late in effector cell differentiation. Finally, suppression was not contingent on the parity of the female or the source of effector cells or of the AF.