A method for preparing antibodies for the treatment of a malignant tumor with inclusion of the particular individual, associated immune system, comprising (a) determining the individual communication structure between the malignant tumor and the immune system, comprising - determining at least one expression pattern of multiple embryonic HLA groups present on the malignant tumor, wherein the embryonic HLA groups comprise HLA-E, HLA-F and HLA-G and wherein the determining of the expression pattern comprises checking whether the embryonic HLA groups are expressed, and - determining, based on the determined expression pattern, at least one receptor type present on/in immunocompetent cells of the immune system which type is capable of bonding at least a part of the expressed embryonic HLA groups as ligand and, based on this bond, of exerting an inhibitory effect on the immunocompetent cells, and (b) providing antibodies of the type which - specifically bond as ligands to the at least one determined receptor type and as a result block or mask the receptor in such a manner that the at least one part of the expressed HLA groups cannot bond there or can only bond there with a lesser effect, - but do not inhibit the associated immunocompetent cell themselves. (a) determining the individual communication structure between the malignant tumor and the immune system, comprising - determining at least one expression pattern of multiple embryonic HLA groups present on the malignant tumor, wherein the embryonic HLA groups comprise HLA-E, HLA-F and HLA-G and wherein the determining of the expression pattern comprises checking whether the embryonic HLA groups are expressed, and - determining, based on the determined expression pattern, at least one receptor type present on/in immunocompetent cells of the immune system which type is capable of bonding at least a part of the expressed embryonic HLA groups as ligand and, based on this bond, of exerting an inhibitory effect on the immunocompetent cells, and - determining at least one expression pattern of multiple embryonic HLA groups present on the malignant tumor, wherein the embryonic HLA groups comprise HLA-E, HLA-F and HLA-G and wherein the determining of the expression pattern comprises checking whether the embryonic HLA groups are expressed, and - determining, based on the determined expression pattern, at least one receptor type present on/in immunocompetent cells of the immune system which type is capable of bonding at least a part of the expressed embryonic HLA groups as ligand and, based on this bond, of exerting an inhibitory effect on the immunocompetent cells, and (b) providing antibodies of the type which - specifically bond as ligands to the at least one determined receptor type and as a result block or mask the receptor in such a manner that the at least one part of the expressed HLA groups cannot bond there or can only bond there with a lesser effect, - but do not inhibit the associated immunocompetent cell themselves. - specifically bond as ligands to the at least one determined receptor type and as a result block or mask the receptor in such a manner that the at least one part of the expressed HLA groups cannot bond there or can only bond there with a lesser effect, - but do not inhibit the associated immunocompetent cell themselves.