IN-VITRO CYTOSTATIC EFFECT OF TNF (TUMOR-NECROSIS-FACTOR) ENTRAPPED IN IMMUNOLIPOSOMES ON CELLS NORMALLY INSENSITIVE TO TNF

The cytostatic activity of TNF entrapped in novel immunoliposomes with a specific antibody against target cells is described. A two step con jugation method was used for the preparation of these targeted immunol iposomes. In the first step, liposomes containing N-4-(p-maleimidophen yl)butyryl phosphatidylethanolamine (MPB-PE) were conjugated with a go at anti-mouse IgG Fab' fragment which recognizes the Fc portion of a m ouse antibody against the target cell markers. In the second step, the mouse antibody against human tumor cells was conjugated to the liposo mes. Using these targeted immunoliposomes, we demonstrated that cells usually insensitive to TNF such as Daudi cells, MT-2 cells and T-24 ce lls could become sensitive to TNF in vitro. The cytostatic activity of these immunoliposomes was blocked by the addition of a lysosomotropic agent such as NH4Cl or chloroquine. Significant uptake of I-125-TNF i nto T-24 cells was observed when these immunoliposomes were used, and this uptake of TNF was inhibited by cytochalasin B or chloroquine. Fre e I-125-TNF was not taken up by these cells.