A method of producing monoclonal antibodies that bind to tumor-associated gangliosides, the method comprising: (1) immunizing a host with tumor cells; (2) boosting the host with a suspension comprising a mixture of tumor cell membrane and at least one purified lactonized tumor-associated ganglioside; (3) boosting the host with an immunogen comprising a lactone of a tumor associated ganglioside adsorbed on or incorporated into a carrier; (4) fusing immunized cells from the host with myeloma cells to form hybridoma cells; (5) selecting hybridoma cells that produce antibody that binds to the ganglioside of step (3); (6) culturing the selected hybridoma cells; and (7) recovering the antibody.