Flow cytometric analysis of anti-platelet antibodies in patients with chronic idiopathic thrombocytopenic purpura (ITP) using acid-treated, formalin-fixed platelets.

Acid treatment of normal washed platelets prepared by albumin density gradient centrifugation followed by formalin fixation effectively eliminates HLA class I antigens from the platelet surface, without altering the immunoreactivity of platelet membrane glycoproteins Ib and IIb/IIIa complex. Using these platelets, flow cytometric analysis was performed on a total of 20 sera from different patients with chronic ITP, and revealed an inverse linear correlation between the platelet count and the mean fluorescence intensity which represents a relative amount of platelet-bound IgG. These results suggest that acid-treated, formalin-fixed platelets can be used as specimens to detect anti-platelet antibodies to differentiate from those to HLA-class I antigens.