Concentration-dependent processing of initiator (caspase-9 and -8) and the executioner (caspase-3) caspases was also observed, indicating that the intrinsic and the extrinsic pathways play an important role in the mechanism of cell death.
The extrinsic pathway is triggered when death ligands bind to their respective cell surface death receptors through recruitment of FAS-associated death domain (FADD) protein, procaspase-8 through the formation of a complex that induces cell death and activation of the caspases (caspase-8 and caspase-10).
In this paper, we describe the extrinsic pathway which are activated by death receptors like the tumour necrosis factor receptor (Fas receptor -APO-1 or CD95) that belongs to TNF receptor super family .
Although the intrinsic pathway involves early activation of caspase-9, and the extrinsic pathway is mediated through caspase-8, both lead to activation of the "executioner" caspase-3 and a variety of proteases and endonucleases.
We assume that membrane phospholipids exposed by the slight erythrocytolysis may compete with the PT reagent (thromboplastin) used for the assay of extrinsic pathway factors, causing prolongation of PT.