Induction of syngeneic tumour-specific immunity by liposomes reconstituted with L₂C tumour-cell antigens

Liposomes composed of phosphatidylcholine and phosphatidylserine were reconstituted by detergent dialysis with 3 M KCl extracts of L₂C tumour cells. Liposomes containing L₂C antigens were as antigenic as intact tumour cells in the elicitation of delayed-type hypersensitivity responses in strain-2 guinea-pigs previously immunized against L₂C tumours. Soluble L₂C antigens were devoid of immunoprotective activity, whereas the reconstituted liposomes were capable of protecting animals against up to approximately 100 times the minimal lethal dose of tumour cells. Moreover, the reconstituted liposomes were as antigenic and immunoprotective as viable (irradiated) cells.