Dimethylsulphoxide induction of the murine macrophage-like line P388D1: change of phagocytic ability and cell surface properties.

The murine macrophage-like cell line P388D1 ingests immunoglobulin-coated sheep red cells (IgG-SRC) poorly, but after 3 days incubation in the presence of 1.5% dimethyl sulphoxide (DMSO), it becomes highly phagocytic. We used this model to correlate triggering of phagocytosis with some surface properties of P388D1 cells, possibly involved in recognition or engulfment of particles. The accessibility of Fc receptors on the cell membranes did not seem to be affected by DMSO treatment since the binding of IgG-SRC to cells was the same before and after treatment with DMSO. A technique allowing quantitative determination of the stability of cell-particle binding showed that binding strength was not the only essential factor in triggering ingestion. Hydrophobicity and surface charge were postulated to play a role in phagocytic recognition. No change in hydrophobicity, as assayed by contact-angle measurement, and in net surface charge evaluated by cell electrophoresis, was observed for normal and DMSO-treated P388D1 cells. On the other hand, the fluorescence polarization of a membrane lipophilic probe (1,6-diphenyl-1,3,5-hexatriene) was significantly (P less than 0.01) decreased when P388D1 cells were treated with DMSO. Since the effect of DMSO on P388D1 function was delayed, our results were consistent with the view that enhancement of phagocytosis might be a consequence of some modification of membrane dynamics, due to changes in lipid composition.