Markers of platelet activation and platelet-leukocyte interaction in patients with myeloproliferative syndromes.
BACKGROUND
Changes in platelet count and function contribute to thrombo-hemorrhagic episodes in chronic myeloproliferative syndromes (MPS). We used flow cytometry to study platelet-leukocyte conjugates and markers of platelet activation in patients with MPS.


METHODS
Whole blood from patients with chronic myelogenous leukemia (CML), polycythemia vera (PV), chronic myelofibrosis (MF), and essential thrombocythemia (ET) and from healthy volunteers was prepared for flow cytometry. Platelet microparticles and platelet microaggregates were identified with anti-CD42b and forward scatter, activated platelets with anti-CD62p. Anti-CD42b, anti-CD14, and anti-CD45 were used to study platelet-leukocyte conjugates.


RESULTS
The percentage of CD62p-positive platelets was elevated in all myeloproliferate syndrome subtypes. The median percentage of platelet microparticles was 5.2% in controls and significantly higher in PV (12.0%), MF (11.0%), and ET (11.0%, all p<0.05). There was an increased percentage of platelet-neutrophil conjugates in patients with PV (8.3%) and ET (10.4%) compared to normal controls (6.8%, all p<0.05). Platelet-monocyte conjugates were 8.0% in controls and elevated in PV (15.4%) and ET (15.0%, all p<0.05). Patients with a history of venous or arterial thrombotic events had slightly less platelet-leukocyte conjugates and slightly more microparticles than patients without thrombosis; however, this difference was not statistically significant.


CONCLUSIONS
These findings suggest that platelet-leukocyte conjugate formation occurs in myeloproliferative syndromes and indicates platelet activation. Also, platelet microparticles are elevated and might provide a catalytic surface for thrombin generation. This could explain the clinical observation that patients with myeloproliferative syndromes have an increased risk to experience arterial or venous thrombotic events.
Villmow
Torben
T
Department of Hematology/Oncology, Faculty of Internal Medicine, Justus-Liebig-University, Klinikstr. 36, 35385 Giessen, Germany.
Kemkes-Matthes
Bettina
B
Matzdorff
Axel C
AC
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000097:blood; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000097:blood; D017493:Leukocyte Common Antigens / Q000097:blood; D007962:Leukocytes / Q000276:immunology / Q000502:physiology*; D018950:Lipopolysaccharide Receptors / Q000097:blood; D008297:Male; D008875:Middle Aged; D009196:Myeloproliferative Disorders / Q000097:blood*; D019007:P-Selectin / Q000097:blood; D015539:Platelet Activation / Q000276:immunology; D019038:Platelet Glycoprotein GPIb-IX Complex / Q000378:metabolism; D011087:Polycythemia Vera / Q000097:blood; D055728:Primary Myelofibrosis / Q000097:blood; D013920:Thrombocythemia, Essential / Q000097:blood
D015415:Biomarkers; D018950:Lipopolysaccharide Receptors; D019007:P-Selectin; D019038:Platelet Glycoprotein GPIb-IX Complex; D017493:Leukocyte Common Antigens