The immunomodulatory activity of human amniotic fluid can be correlated with transforming growth factor-beta 1 (TGF-β1) and β2 activity

Abstract

The role of alphafetoprotein (AFP) in the immunomodulatory activity of amniotic fluids (AE) from normally progressing human pregnancy (weeks 14–16) was investigated. A panel or42 AF (25% v/v) reduced significantly phytohaemagglutinin (PHA)-induced peripheral blood mononuclear cell (PBMC) proliferation in serum-free cultures with a mean per cent inhibition of 68·4 ± 5·5%. In contrast, AEP preparations, with one exception (U.AFP), failed to display inhibitory activity. Pretreatment of AF with anti-TGF-β1 and β2 antibodies used alone resulted in the mean per cent loss of inhibition of 33·1 ± 3·9% and 52·3 ± 7·5%, respectively. A summative loss of AF-mediated inhibition was detected when anti-TGF-β1 and β2 antibodies were used in combination, but immunomodulation was rarely abolished 100% by this treatment. Anti-TGE-β2 antibody treatment, unlike anti-TGF-β1 antibody treatment, reversed the inhibitory activity of U.AFP. The amount of TGF-β1 and β2 contained in human AF was studied by growth inhibition of Mv1 Lu cells. The mean levels of TGF-β1 and β2 in AF were 11 ± 0·9 U/ml and 2·3 ± 0·4 U/mI, respectively, which corresponds with a mean per cent inhibition of 49 ±4·7%. U.AFP also significantly inhibited Mv1 Lu cell growth. To investigate the mechanism of AF-mediated inhibition, the effect of AF and AEP on IL-2 production by concanavalin A (Con A)-stimulated PBMC blasts was determined by the CTLL-2 cell bioassay. IL-2 production was reduced 55·5% in AF-treated blasts and 61% in U.AEP-treated blasts compared with controls. Our findings indicate that the immunomodulatory activity of human AF can be correlated with TGE-β1 and β2 and not with AFP, the inhibitory activity of U.AFP preparation reflecting copurifying TGF-β2 activity.