Interactions of mannose binding-lectin with red blood cells by employing cationic quantum dots

Mannose-binding lectin (MBL) plays important roles by interacting with specific molecular patterns on cell surfaces, triggering first-line host defense. We investigated the MBL interaction with healthy red blood cell membranes as well as its effects on the membrane rheology. We explored electrostatic interactions between cationic quantum dots (QDs) and negatively charged red blood cell surfaces to quantitatively evaluate membrane electrical charges as well as to investigate the MBL binding to healthy erythrocytes. Results showed that cationic QDs labeled efficiently red blood cells. However, the MBL interaction with erythrocytes prevents the QD labeling. We also observed that red blood cells treated with MBL are more resistant to lysis, suggesting a membrane-stabilizing effect. Moreover, we used a fluorescent anti-MBL antibody and Candida albicans cells to further study the MBL interaction with erythrocytes. Our results of this comparative labeling suggested that either this probe was not effective to detect MBL bound to healthy red blood cells (by its carbohydrate-recognition domain) or the MBL binding to those cells might be occurring via another portion. Thus, our results demonstrated the ability of MBL interacting with healthy red blood cells and pointed out to a new role of this protein as a membrane-stabilizing molecule.