The effects of mouse alpha-fetoprotein on T-cell-dependent and T-cell-independent immune responses in vitro.

Mouse alpha-fetoprotein (AFP) suppressed the specific antibody response to the T-cell-dependent antigen sheep erythrocytes (SRBC) and the phytohemagglutinin- and concanavalin-A-stimulated DNA synthesis of purified T lymphocytes but failed to inhibit the T-cell-independent antibody response to dinitrophenyl-substituted Ficoll (DNP-Ficoll) and the lipopolysaccharide-stimulated polyclonal B-cell antibody synthesis. Mouse amniotic fluid (MAF) suppressed antibody responses to both T-cell-dependent and T-cell-independent antigens; however, the effects could be differentiated since dialysis of the MAF removed most of the suppressive effect on the DNP-Ficoll response but did not diminish the inhibitory action on the anti-SRBC response. The results indicate that AFP suppresses certain T-lymphocyte functions in vitro and does not act by directly inhibiting B-cell functions.