[Study on platelet satellitism].

The platelet leukocyte adherence phenomenon, so-called 'Platelet Satellitism (PS)', was recognized on peripheral blood smear from ethylenediaminetetraacetic acid (EDTA)-anticoagulated blood in two patients. The present study was undertaken to elucidate both inducing and inhibitory factors for PS by utilizing two patients' blood. Both heparin and sodium citrate could not induce PS in these patients. This phenomenon was inhibited by anti-platelet membrane glycoprotein (GP) IIb/IIIa complex antibody (AP-2), but not by antibodies against platelet membrane glycoprotein (GP) Ib/IX complex, fibrinogen and von Willeb and factor. Patients' sera were subjected to column chromatography of Sephacryl S-300 to obtain immunoglobulin (Ig) G, IgA and IgM fractions. In one patient, IgG fraction, but neither IgA nor IgM fractions could induce PS phenomenon in normal whole blood, while IgA but neither IgG nor IgM could induce PS in another patient. Furthermore, when purified IgG from the first patient was treated with 2U/ml of plasmin to digest Fc portion, PS phenomenon disappeared. The F(ab')2 portion was prepared from whole IgG treated with pepsin, then added to normal whole blood. Purified F(ab')2 fragment by itself could not induce PS phenomenon, whereas the preincubation of F(ab')2 in normal whole blood could inhibit the PS caused by the patient's whole IgG. These results indicate that platelet membrane glycoprotein (GP) IIb/IIIa complex and both Fab and Fc portions of immunoglobulin might be necessary to induce PS phenomenon in EDTA-anticoagulated whole blood.