Biomedical Engineering Reference
In-Depth Information
12
Recombinant blood products and
therapeutic enzymes
12.1 Introduction
Blood and blood products constitute a major group of traditional biologics. The main components
of blood are the red and white blood cells, along with platelets and the plasma in which these cel-
lular elements are suspended. Whole blood remains in routine therapeutic use, as do red blood cell
and platelet concentrates. A variety of therapeutically important blood proteins also continue to
be purifi ed from plasma. These include various clotting factors and immunoglobulins. However,
in keeping with the scope of this topic, we focus in this chapter upon blood proteins/blood-related
proteins produced by genetic engineering. These include recombinant coagulation factors, antico-
agulants (such as hirudin) and thrombolytics (such as tPA). Also considered towards the end of the
chapter are a number of recombinant enzymes that have found therapeutic application.
12.2 Haemostasis
Blood plays various vital roles within the body and it is not surprising that a number of processes
have evolved capable of effectively maintaining haemostasis (the rapid arrest of blood loss upon
vascular damage, in order to maintain a relatively constant blood volume). In humans, three main
mechanisms underline the haemostatic process:
•
The congregation and clumping of blood platelets at the site of vascular injury, thus effectively
plugging the site of blood leakage.
•
Localized constriction of the blood vessel, which minimizes further blood fl ow through the
area.
•
Induction of the blood coagulation cascade. This culminates in the conversion of a soluble
serum protein, fi brinogen, into insoluble fi brin. Fibrin monomers then aggregate at the site of
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