Differential sialylation regulates the apoptotic activity of glycodelin A

Glycodelin A (GdA), a dimeric lipocalin, expressed by the uterine endometrium, is an immunomodulatory agent and induces apoptosis in T-cells. In this study we demonstrate that two populations of GdA with subtle differences in their net ionic charge are present in the amniotic fluid and that, apoptotic activity is exhibited only by the population with more sialic acid residues. Significantly, removal of sialic acid residues from the active populations of GdA abrogates the activity of the molecule, suggesting that the extent of sialylation might be a factor regulating the activity of GdA.