Role of macromolecular depletion in red blood cell adhesion

The adhesion of red blood cells (RBCs) to cells or surfaces is of current basic science and clinical interest yet the details governing this process are still being explored. In this study, the effects of nonadsorbing polymers on the adhesion of RBC to albumin-coated glass have been investigated employing interference reflection microscopy. Our experimental results indicate that adhesion can be induced in the presence of dextran with a molecular mass >or=70 kDa and that the induced forces are strong enough to significantly suppress membrane undulations. The overall dependence of the adhesion energies on the polymer concentration is consistent with the assumption that macromolecular depletion induces this attractive interaction. In conclusion, our results indicate that depletion interaction might play a significant role in RBC adhesion via initiating close contacts, and thus suggest the importance of depletion forces for RBC interactions and its relevance to a wide variety of in vitro and in vivo cell-cell and cell-surface interactions.