The present invention refers to a method for obtaining a cell culture supernatant or a fraction thereof having a specific tumor antigen peptide repertoire having the steps of: a) exposing in suitable conditions a tumor cell culture expressing the specific tumor antigen peptide repertoire to a Pattern Recognition Receptor (PRR) agonist and/or to one inflammatory cytokine to increase the opening of connexin-hemichannels (CxH); b) collecting the cell culture supernatant; and c) optionally obtaining a fraction of the supernatant, wherein the supernatant has MHC class I and MHC class II peptides and non-classical MHC molecules (HLA-E).