Suppression of the primary cell-mediated immune response by human alpha1-fetoprotein in vitro.

A possible immunoregulatory role of human α₁-fetoprotein (HAFP) was investigated. HAFP-enriched fractions as well as pure HAFP were obtained by means of two different procedures, as follows. After passage of HAFP-containing ascites of patients with primary liver carcinoma (PLC) on an anti-HAFP immunosorbent column, the retained proteins were eluted first by a glycine-NaOH buffer, pH 10.0 (resulting in HAFP I), and second by NaSCN (HAFP II). HAFP was further purified by passage of the HAFP-containing fractions an on anti-human whole serum (anti-HWS) immunosorbent column. This resulted in semipurified HAFP I and II. HAFP, pure by means of SDS-disc gel electrophoresis, Ouchterlony gel diffusion, and immunoelectrophoresis, was obtained by recycling on the anti-HWS immunosorbent column, as well as by a final Sephadex G-100 gel filtration. A possible immunoregulatory activity was assessed by testing the influence of semipurified as well as pure HAFP I and II on the uptake of tritiated thymidine by human lymphocytes stimulated by allogeneic lymphocytes in vitro. Only HAFP I, semipurified as well as pure, consistently exerted a profound suppressive effect on this primary cell-mediated immune response at concentrations of 150–200 μg/ml. In contrast, HAFP II did not show a comparable immunoregulatory effect either because there are two biologically different HAFPs or because of a loss of biological activity from HAFP II due to the use of the sodium thiocyanate elution technique.