Platelet-associated immunoglobulins in patients with primary Sj?gren's syndrome

Ten patients with primary Sj?gren's syndrome (7 females) were examined in order to evaluate whether in vivo-bound platelet-associated immunoglobulins (PAIg) and/or in vitro binding of circulating Ig to normal platelets influences platelet function. With an ELISA technique it was found that 9/10 patients had increased amounts of in vivo PAIgG, 4/10 patients of in vivo PAIgA and 5/10 patients of in vivo PAIgM. There was no correlation between patients platelet aggregability and the presence of in vivo PAIg. Incubation of platelets from a healthy person with plasma from the 10 patients caused in vitro binding of IgG in 7/10 cases, of IgA in 0/10 cases and of IgM in 1/10 cases. Adenosine diphosphate (ADP)-induced aggregability of the normal platelets was impaired in 7/10 incubation experiments (no correlation to in vitro PAIg) and unchanged in 3/10 cases. Epinephrine- and collagen-induced platelet aggregability was unchanged in all cases. It is concluded that increased amounts of in vivo and in vitro PAIg seem to occur frequently in patients with primary Sj?gren's syndrome, but do not influence platelet aggregability.