J. Cell Sci. 64, 281-293 (1983) 281 Printed in Great Britain © The Company of Biologists Limited 1983 DIMETHYLSULPHOXIDE INDUCTION OF THE MURINE MACROPHAGE-LIKE LINE P388D1: CHANGE OF PHAGOCYTIC ABILITY AND CELL SURFACE PROPERTIES CHRISTIAN CAPO 1 '*, ZOHAIR MISHAL 2 , VINCENT BALLOY 1 , ANNE-MARIE BENOLIEL 1 AND PIERRE BONGRAND 1 1 Laboratoire d'Immunologie (Pr. DEPIEDS), Hopital Sainte Marguerite, B.P29, 13277 Marseille Cedex 09, France 1 Centre d'Immunologie INSERM-CNRS de Marsetlle-Luminy, Case 906, 13288 Marseille Cedex 09, France SUMMARY 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 bind- ing showed that binding strength was not the only essential factor in triggering ingestion. Hydro- phobicity 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 (l,6-diphenyl-l,3,5-hexatriene) was significantly (P < 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 enhance- ment of phagocytosis might be a consequence of some modification of membrane dynamics, due to changes in lipid composition. INTRODUCTION Cells of the mouse tumour line P388D1 possess most macrophage characteristics: they adhere to glass and plastic, they may express la antigens and induce T killer cells, they are cytotoxic and phagocytose latex beads (for a review, see Ralph, 1981). These cells carry surface receptors for immunoglobulin G (Fc y-R) (Haeffner-Cavaillon, Klein & Dorrington, 1979) and form rosettes with IgG-coated-erythrocytes (IgG- SRC) (Koren, Handwerger & Wunderlich, 1975), but they were reported to ingest immunoglobulin-coated sheep red cells poorly (IgG-SRC) (Snyderman, Pike, Fischer & Koren, 1977). Recently, Takasaki & Leive (1982) substantially enhanced Fc receptor-mediated phagocytosis of sheep red cells by preincubating macrophage- like P388D1 cells with dimethyl sulphoxide (DMSO). DMSO has been previously •Author for correspondence.