The role of human pregnancy specific P1-glycoprotein in the phenotypic maturation of NK-, and NKT-cells

Effect of human pregnancy specific Р 1-glycoprotein (PSG) in physiological concentrations was analyzed against the expression of natural killer (NK)-, T-cells with natural killer functions (NKT-) in in vitro model using female peripheral cells. The study used PSG preparation being obtained with the authors' methodology and identified by LS/MC method. This preparation was made of several molecular forms of the protein namely PSG-1, PSG-3, PSG-7, PSG-9, as well as some isoforms and precursors detectable in vivo. In general, this preparation maximally approaches the isoform composition of PSG in the serum of a pregnant woman. It was revealed that PSG in high concentration (100 ug/ml) suppressed the CD16/56 expression by NK-cells, while inhibiting the cytolytic activity of these cells. Apparently, PSG suppressing effect against NK cell expression of CD16/56 may have role in semiallogenic fetus protection from the attack of cytotoxic NK cells. Meanwhile, PSG in low concentrations (1 and 10 ug/ml) enhanced the CD16/56 expression by NKT-cells that was related to the cytokine-producing activity. It is possible that PSG effects being revealed relatively to NKT cells are one of probable mechanisms of PSG involvement in maintaining of cytokine balance and formation of peripheral tolerance in pregnancy. Collectively, results obtained demonstrate new immunomodulating effects of pregnancy-specific Р1 -glycoprotein.