Effect of Cytokines and Chemokines on Sickle Neutrophil Adhesion to Fibronectin

Abstract

A role for leukocytes in sickle cell vaso-occlusive crisis is becoming increasingly recognized. Neutrophil counts are higher in sickle cell patients and neutrophils from these patients demonstrate increased adhesion to endothelial monolayers under certain circumstances. The effects of selected cytokines on the adhesion mechanisms of normal neutrophils and neutrophils from sickle cell anaemia patients (SCA neutrophils) were investigated. Neutrophils were separated from the blood of homozygous (HbSS) SCA patients and healthy controls. Following pre-incubation (25 min, 37°C) of the cells with cytokines, the adhesion of the cells to fibronectin (FN)-coated plates (20 µg/ml) was determined (60 min, 37°C, 5% CO₂). Basal adhesion of normal and SCA neutrophils to FN was not statistically different. Pretreatment of normal neutrophils with either IL-6 (10–100 pg/ml), GCSF (1– 10 ng/ml) or IL-8 (1–100 ng/ml) had no significant effect upon their adhesion to FN. In contrast, SCA neutrophil adhesion to FN was increased significantly following pre-incubation with IL-6, G-CSF and IL-8 (p < 0.01). RANTES (1–100 ng/ml) had no significant effect on either normal or SCA neutrophil adhesion to FN. Flow-cytometric analyses demonstrated that IL-8 (10 ng/ml) significantly augments CD11b (Mac-1 integrin subunit) expression on SCA neutrophils, but not normal neutrophils. IL-6 and G-CSF (10 pg/ml and 10 ng/ml, respectively), however, had no effect on SCA neutrophil adhesion molecule expression. In conclusion, SCA neutrophil adhesion mechanisms may increase in the presence of certain cytokines, in vivo, and this activation may contribute to the physiopathology of sickle cell disease.