The Yin-Yang of thrombin and activated protein C.

The concepts of Yin and Yang provided the intellectual framework of much of Chinese scientific thinking, especially in the fields of biology and medicine. The organs of the body were seen to be inter-related and their functions could be best appreciated through understanding connections and correlations, in the same way as in other naturally occurring phenomena. Although this principle is recognizable within our current understanding of pro- and anti-coagulant mechanisms, the literature in this field seldom conveys the unifying nature of its overall structure. Considering the coagulation cascade and the anticoagulant system as opposing but complementary forces would be central to the concept of Yin and Yang. This article is presented along such lines with a focus on thrombin and activated protein C (APC) as key examples of that balancing axis in maintaining haemostatic harmony. The emphasis will be on how understanding this relationship at the molecular and cellular level holds promise in the translation to improved clinical care.