Monocyte procoagulant activity: development of a microtitre plate chromogenic assay.

A monocyte procoagulant assay was developed based on the original method of Surprenant and Zuckerman, which quantitates a factor Xa-specific chromogenic substrate (at 405 nm) activated via the extrinsic coagulation pathway. Normal tissue factor initiation of the pathway is replaced by tissue factor generated from monocytes, stimulated by various agents including bacterial lipopolysaccharide, and antibody/antigen complexes. Hydrolysis of the chromogenic substrate is therefore directly proportional to the degree of monocyte activation. Using a chromogenic substrate as an end-point the assay was performed in a standard microtitre plate.