Submitted October 2, 2006
Accepted April 3, 2007
Increased adhesion to endothelial cells of erythrocytes from patients with Polycythemia Vera is mediated by laminin alpha5 chain and Lu/BCAM
Marie-Paule Wautier, Wassim El Nemer, Pierre Gane, Jean-Didier Rain, Jean-Pierre Cartron, Yves Colin, Caroline Le Van Kim, and Jean-Luc Wautier*
U665, INSERM, Paris, France
Nuclear Medecine, Universite PARIS7/Denis Diderot, UFR Medecine, Paris, France
Institut National de la Transfusion Sanguine, Paris, France
* Corresponding author; email: jlwautier{at}ints.fr.
Patients with Polycythemia Vera (PV) have a JAK2 mutation and an increased risk of vascular thrombosis which is related to red blood cell (RBC) mass and platelet activation. We investigated functional RBC abnormalities, which could be involved in thrombosis. RBC adhesion to human umbilical vein endothelial cells (HUVEC) was measured by a radiometric technique and in a flow system by video microscopy and adhesion molecule expression was determined using specific antibodies (against CD36, CD49d, ICAM-4, Lu/BCAM, CD147 and CD47) and flow cytometry in a group of 38 PV patients and of 36 normal subjects. Adhesion of PV RBC was increased 3.7 fold compared to normal RBC (p<0.001). The adhesion was inhibited when PV RBC were incubated with anti-Lu/BCAM or when HUVEC were treated with anti-laminin 
5 and to a lower extent with anti-3 integrin. Lu/BCAM was slightly increased in expression and constitutively phosphorylated in PV RBC. Transfection of K562 cells with JAK2 V617F resulted in an increased expression and phosphorylation of Lu/BCAM. Phosphorylation of LU/BCAM is known to increase RBC adhesion. Our results indicated that JAK2 mutation may be linked to Lu/BCAM modification and increase RBC adhesiveness which may be a factor favouring thrombosis in PV.
