Efforts to get a strong and sustained anti-tumour immune response induced by a tumour specific antigen have failed, but sipuleucel-T has been approved by the US Food and Drug Administration (FDA). We noticed that exosomes secreted by tumour cells or immune cells may be crucially involved in the tumour immune response, whereas others have had inconsistent findings on exosome involvement. Based on immune network theory, we summarise research advances of exosomes and speculate that in the tumour immune response exosomes follow the immune response curve hypothesis. Exosomes activate simultabeously both immune activation and immune tolerance, but at different intensities. To obtain a desired anti-immune response, the initial point of immunity should be determined to achieve the strongest anti-tumour response, and repeated in vitro to extend and enhance this response. As a result, our hypothesis proposes that studies should now be directed at determining the exact time of exosome activity in maintaining a viable anti-tumour immune response in vivo.