Transcripts
DR. ROCK:
Now, over the years, since 1924,
there have been a large number of agents,
reagents, that have been considered to be
responsible for the disease.
A variety of platelet
aggregating factors have been identified; these
include the 37 Kd protein of Rinad (phonetic)
and his group from Miami.
Several years ago John Calpain
and his group from McMaster University in
Hamilton identified an enzyme, calpain, which is
active against von Willebrand. And we know that von Willebrand
factor is a very critical element, first of all,
in the clots that are formed in these disorders,
and secondly, von Willebrand factor has an
important role in platelet aggregation.
Joel Moake out of Texas has
reported in four cases of chronic TTP the
presence of very large, unusually large, von
Willebrand factor forms in the plasma of these
patients. And while von Willebrand factor
normally is responsible for causing platelets to
stick to the subendothelium, these unusually
large forms are even more active and have a
propensity for accumulating proteins or platelets
far more quickly and effectively than does the
normal protein.
For many years other
investigators have reported the presence of
antibodies in these patients' serum, antibodies
directed against platelets, and also antibodies
against endothelial cells.
Then more recently the works of
Tsai and Furlan have shown an antibody against
the metalloprotease. And what this is, is an
antibody that -- I see what happens, it does
work on the wall and on the floor, but not on
the screen, in particular, okay -- these
antibodies inhibit the normal breakdown of von
Willebrand factor resulting in the fact that the
plasma has more of the larger forms of von
Willebrand factor present in the plasma.
Dr. Tsai visited us recently in
Ottawa at a meeting educating the Apheresis group
and claims that he finds these antibodies in the
majority of patients presenting with TTP. As I
will show you later in my presentation, we have
found this to be variably so.
