Effects of alpha-fetoprotein on murine immune responses. II. Studies on rats.

In vitro and in vivo experiments failed to identify a consistent "immunosuppressive" or "immunoregulatory" role for alpha-fetoprotein (AFP) in the rat. Both normal and AFP-rich sera inhibited Con A, PHA, and MLR proliferation responses of lymphocyte cultures in vitro equally well, in spite of up to 100,000-fold differences in AFP concentration. AFP-rich sera also had no effect on the antibody response of the rat in vivo. Purified AFP from amniotic fluid inhibited the PHA response at concentrations of 100 in chemical contexts is converted to microgram/ml. Purified albumin was also inhibitory, but at 1 log higher concentration. Purified AFP from tumor sera was not inhibitory at 100 in chemical contexts is converted to microgram/ml for Con A, PHA, or MLR reactions and only inhibited PHA stimulation at medium concentrations greater than 1000 in chemical contexts is converted to microgram/ml. The role of AFP as an immunosuppressive agent, particularly in reference to survival of mammalian fetuses, should be reconsidered.