Inhibition of human lymphocyte transformation by human alpha-fetoprotein (HAFP); HAFP monomers and multimers and a resistant lymphocyte subpopulation.

We have previously shown that human alpha-fetoprotein (HAFP) inhibits the response in vitro of human lymphocytes to a variety of mitogenic stimuli. In this report we present evidence that HAFP preparations containing dimeric and trimeric forms are no more inhibitory than HAFP monomeric isolates. HAFP isolates of low inhibitory potency cannot impede the capacity of high-potency HAFP to inhibit lymphocyte transformation. Since lymphocyte responses to phytomitogens or anti-human thymocyte antiserum cannot be totally suppressed by increasing doses of HAFP, we conclude that human lymphocyte preparations contain a population of lymphocytes resistant to the inhibitory action of HAFP.