Characterisation of auto-antibodies against ADAMTS-13 in patients with a history of TTP.

Thrombotic thrombocytopenic purpura (TTP) is a rare and potentially
life-threatening auto-immune disorder, characterised by multiple
micro-angiopathic thrombosis, haemolytic anemia and ischemic organ dysfunction.
In the past years, it has become clear that a deficiency of a von Willebrand
factor cleaving protein, a desintegrin and metalloproteinase with
thrombospondin type 1 motif (ADAMTS-13), is at the basis of the pathogenesis of
TTP (1). It results in the presence of ultralarge molecular weight multimers of
von Willebrand factor (2), which in turn leads to a pro-thrombotic stage where
thrombocyt aggregation is enhanced and microthrombi are formed.

The deficiency of ADAMTS-13 in acquired TTP is thought to be an auto-immune
process: immunoglobulin G antibodies directed against ADAMTS-13 can be found in
all patients with acute TTP. All antibodies are directed against the spacer
domain in ADAMTS-13.

In the current proposal we will investigate the pattern of auto-antibodies in
patients with a history of TTP. It is known that in 50% of these cases
ADAMTS-13 is absent, without any sign of TTP. We hypothesize that antibosies in
this chronic phase are present but directed against other epitopes.

Characterisation of auto-antibodies against ADAMTS-13 in patients with a
history of TTP

Patients will be asked to participate by the Dutch TTP "patiëntenvereniging".
During the yearly contact day ex-TTP patients will be asked to donate 20 ml of
blood and to fill in a short questionaire. It is a cross-sectional study and 50
patients will be included in the following 5 years.

venapunction (20 ml)