Tissue factor expression on monocyte subpopulations during normal pregnancy

Pregnancy is often referred to as a hypercoagulable state due to changes in the haemostatic system. Tissue factor (TF) is the initiator of blood clotting in vivo. The effect of pregnancy on monocyte TF expression was determined in a longitudinal case control study (89 pregnant, 39 non-pregnant). Using whole blood flow cytometry and CD 14 as a monocyte marker, TF expression was measured on all CD 14 positive, CD14(Bright) and CD14(Dim) cells, TF expression was significantly lower in pregnant women than in non-pregnant control subjects, on all CD 14 positive cells at 20 and 35 weeks, on CD14(Bright) cells at 12 and 35 weeks and on CD14(Dim) cells at 20 weeks. Additionally, we report that a higher percentage of CD Will, than CD14(Bright) cells express TF. These results suggest that, in order to maintain homeostasis in haemostasis in an otherwise hypercoagulable state, monocyte TF expression is reduced during, normal pregnancy.