A humanized anti-idiotypic (anti-Id) monoclonal antibody (MoAb) that mimics the disialoganglioside GD2 with potential immunostimulating and antineoplastic activities. Upon administration, monoclonal antibody 4B5 anti-idiotype vaccine may elicit both cellular and humoral immune responses against GD2- expressing tumor cells. GD2 is a glycosphingolipid (ceramide and oligosaccharide) that may be highly expressed by melanomas and other neuroectodermal tumors, while only minimally expressed by normal tissues.