Immunosuppressive Factors in Mouse Amniotic Fluid and Neonate Serum

Abstract

Alpha-fetoprotein (AFP) isolated from neonatal mouse serum (NNS) and mouse amniotic fluid (MAF) was suppressive in both the mixed lymphocyte reaction (MLR) and the lipopolysaccharide-induced (LPS) mitogenesis. On the other hand, AFP-depleted NNS and MAF showed a stronger immunosuppressive effect compared to the oriqinal fluids at the same total protein concentration. These results suggest that proteins other than AFP may also be involved in the net suppressive effect of NNS and MAF in both the T-cell-dependent and T-cell-independent in vitro immune responses. Various AFP preparations resulted in either 1) suppression at concentrations of 5–100 μq: 2) suppression only at high concentrations (100–200 μg); and 3) nonsuppression even at 100–200 μg levels. MLR enhancement was noted with some preparations and was dose dependent; at higher concentrations some enhancing preparations would suppress. Mitogenicity, when present, may obscure suppression. Whether enhancement is a property of a particular species of AFP or a contaminant is unknown. However, the latter seems a distinct possibility since mitogenic substances are shed from columns and some apparently homogeneous AFP preparations are not mitoqenic. AFP from NNS was somewhat more suppressive than AFP from MAF and showed a faster electrophoretic mobility at pH 9.5. These findings suggest that certain subfractions of AFP may be more suppressive than others The net effect of NNS or MAF is dependent on the dose, the test system, the supplemental serum employed, the relative abundance of different AFP variants in the preparation and the presence of a non-AFP suppressive factor(s).