Platelet Physiology
July 19, 2002
09:00 to 13:00
Terrace Room
Boston Park Plaza Hotel
Chairman: A. Koneti Rao, USA
Co-chairs: M. Berndt, Australia; C. Cerletti, Italy; C. Hayward, Canada;
M. Hoffman, USA; A. Michelson, USA;
P. Newman, USA; P. Nurden, France; S. Watson, UK
There were two main themes addressed in this meeting of the Platelet Physiology
Subcommittee. The first one was platelet-leukocyte interactions, an
area where tremendous new information has become available over the last few
years. The second theme was platelet function disorders with a focus
on a specific methodology (Platelet Function Analyzer, PFA-100).
Platelet-Leukocyte Interactions
Several speakers reviewed recent information on different aspects of platelet-leukocyte
interactions. Dr. Bruce Furie reviewed interactions between P-selectin
and PSGL-1. Dr. Jose Lopez reviewed the interactions between GPIb and
MAC-1. Dr. Chiara Cerletti focused on the signaling interactions between
platelets and leucocytes with a focus on Srk kinases. Dr. Michael Berndt
reviewed the regulation of P-selectin binding to PSGL-1 by elastase and cathepsin
G. Lastly, Dr. Alan Michelson reviewed recent information on circulating
monocyte-platelet aggregates as a sensitive marker of in vivo platelet activation
in patients.
Working Group on Platelet Function Disorders
The second half of the session focused on presentations by the Working Group
on Platelet Function Disorders. Despite major advances in our understanding
of platelet physiology and available newer methods, our understanding of the
mechanisms in patients with platelet function disorders remains low.
In the vast majority of patients with inherited abnormalities in platelet
responses, the underlying mechanisms leading to the platelet dysfunction are
unknown. The focus of this session was on the role of PFA-100 in the
diagnosis of platelet function disorders, excluding von Willebrand disease.
PFA-100 has become widely available and is being used in the evaluation and
management of patients with vWD and platelet function disorders.
Dr. Catherine Hayward presented information on developing evidence-based
approaches to the diagnosis of platelet disorders. She presented information
from recent ongoing studies in her laboratory, including the Clinical History
Assessment Tool (CHAT). Several speakers addressed various aspects of PFA-100
in the diagnosis of platelet function disorders (excluding von Willebrand
disease): Drs. Diane Nugent, Marco Cattaneo, Thomas Ortel, Berndt Jilma
and Paul Harrison. The information presented included studies with the PFA-100
in the general group of patients referred for the evaluation of bleeding disorders,
patients with menorrhagia, and those on platelet inhibitory drugs. Following
these presentations, there was a discussion regarding the advantages and
limitations of PFA-100. It was also felt that the working group on
platelet function disorders should continue to explore the need for setting
up collaborations between various laboratories with relevant expertise to
define the underlying mechanisms in patients with inherited disorders of platelet
function.
Dr. James Bussell presented information on the ongoing studies and on the
registry of patients with non-immune thrombocytopenias.