The present invention refers to a method for obtaining a cell culture supernatant or a fraction thereof comprising a specific tumor antigen peptide repertoire comprising the steps of: a) exposing in suitable conditions a tumor cell culture expressing said specific tumor antigen peptide repertoire to at least one 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 said supernatant, wherein said supernatant comprises MHC class I and MHC class II peptides and non-classical MHC molecules (HLA-E).
