Disclosed are methods for preparing a medicament for treating a malignant tumor, along with cell membranes prepared by such methods and the use thereof, in which the individual communication structure between the malignant tumor and the immune system is ascertained based upon a tissue sample containing cells of the malignant tumor by determining a malignant tumor-specific expression pattern of histocompatibility antigens (Human Leucocyte Antigen, HLA) on said tissue sample, masking or removing at least a part of the expression pattern present on the cells of the tissue sample that is capable of exerting an inhibitory effect on immunocompetent cells, and preparing an individual vaccine for eliciting a specific immunological response by lysing those cells on which a part of the expression pattern has been masked or removed.
