Aggregation of mononuclear and red blood cells through an {alpha}4{beta}1-Lu/basal cell adhesion molecule interaction in sickle cell disease.
BACKGROUND
Abnormal interactions between red blood cells, leukocytes and endothelial cells play a critical role in the occurrence of the painful vaso-occlusive crises associated with sickle cell disease. We investigated the interaction between circulating leukocytes and red blood cells which could lead to aggregate formation, enhancing the incidence of vaso-occlusive crises.


METHODS
Blood samples from patients with sickle cell disease (n=25) and healthy subjects (n=5) were analyzed by imaging and classical flow cytometry after density gradient separation. The identity of the cells in the peripheral blood mononuclear cell layer was determined using antibodies directed specifically against white (anti-CD45) or red (anti-glycophorin A) blood cells.


RESULTS
Aggregates between red blood cells and peripheral blood mononuclear cells were visualized in whole blood from patients with sickle cell disease. The aggregation rate was 10-fold higher in these patients than in control subjects. Both mature red blood cells and reticulocytes were involved in these aggregates through their interaction with mononuclear cells, mainly with monocytes. The size of the aggregates was variable, with one mononuclear cell binding to one, two or several red blood cells. Erythroid Lu/basal cell adhesion molecule and α(4)β(1) integrin were involved in aggregate formation. The aggregation rate was lower in patients treated with hydroxycarbamide than in untreated patients.


CONCLUSIONS
Our study gives visual evidence of the existence of circulating red blood cell-peripheral blood mononuclear cell aggregates in patients with sickle cell disease and shows that these aggregates are decreased during hydroxycarbamide treatment. Our results strongly suggest that erythroid Lu/basal cell adhesion molecule proteins are implicated in these aggregates through their interaction with α(4)β(1) integrin on peripheral blood mononuclear cells.
Chaar
Vicky
V
INSERM, UMRS 665, INTS, 6 rue Alexandre Cabanel, 75015 Paris, France. wassim.el-nemer@inserm.fr.
Picot
Julien
J
Renaud
Olivier
O
Bartolucci
Pablo
P
Nzouakou
Ruben
R
Bachir
Dora
D
Galactéros
Frédéric
F
Colin
Yves
Y
Le Van Kim
Caroline
C
El Nemer
Wassim
W
D000328:Adult; D000755:Anemia, Sickle Cell / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D000986:Antisickling Agents / Q000008:administration & dosage; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D002449:Cell Aggregation / Q000187:drug effects; D002478:Cells, Cultured; D018920:Coculture Techniques; D004912:Erythrocytes / Q000378:metabolism* / Q000473:pathology; D005260:Female; D006801:Humans; D006918:Hydroxyurea / Q000008:administration & dosage; D039041:Integrin alpha4beta1 / Q000378:metabolism*; D008188:Lutheran Blood-Group System / Q000378:metabolism*; D008297:Male; D009000:Monocytes / Q000378:metabolism* / Q000473:pathology
D000986:Antisickling Agents; C090228:BCAM protein, human; D015815:Cell Adhesion Molecules; D039041:Integrin alpha4beta1; D008188:Lutheran Blood-Group System; D006918:Hydroxyurea