Non-specific binding by macrophages: evaluation of the influence of medium-range electrostatic repulsion and...

Rat peritoneal macrophages can bind glutaraldehyde-treated human rat cells (GHRC), but not normal human red cells (HRC). When the surface charge of HRC was reduced by treating them with neuraminidase (to remove some negative sialic acid residues) or coating them with polylysine (a positively charged polymer), no substantial binding to macrophages was obtained. However, a similar reduction of the surface charge of GHRC resulted in sevenfold enhancement of their binding of macrophages. All erythrocyte batches were tested with a phase partition technique: only glutaraldehyde-treated cells were found hydrophobic. It is concluded that: i) Short range hydrophobic interactions are responsible for macrophage-GSRC adhesion. ii) Medium range electrostatic repulsion may substantially hamper any close approach of the macrophage and particle surface in physiological conditions.