An IgG antibody which developed in a polytransfused thrombasthenic patient reacted
in complement fixation with platelets from 350 normal individuals but not with platelets
from 8 other thrombasthenic patients. It agglutinates human platelets in PRP but not
thrombasthenic platelets. This agglutination increased if the PRP was preincubated
at 37°C or if the platelets were isolated before the addition of the antibody. Dog
but not rabbit platelets are agglutinated by the patient plasma. Neither adenosine,
nor PGE1 inhibit this agglutination which is slightly reduced by acetylsalicilic acid
and disappears with EDTA and EGTA (3,8 mM).
Its activity is reduced or abolished after incubation with control platelet membranes
but not with those obtained fron) thrombasthenic or rabbit platelets.
It does not inhibit the ADP-induced shape change of normal platelets, and it prevents
all the ADP mediated platelet aggregations but, not those induced by bovine factor
VIII and ristocetin.
This antibody seemed to be directed against a molecule absent or structurally modified
in thrombasthenic platelets which would be involved in platelet aggregation and more
especially in ADP mediated platelet aggregation.
