Microvesicles (MV) or exosomes are produced and secreted by tumor and normal cells. The molecular profile and functions of tumor-derived vs dendritic cell (DC)-derived MV are distinct. The former express death ligands and mediate apoptosis of activated T cells. The latter promote CD4+ T cell proliferation and may play a role in regulating T cell responses. Serving as intercellular communication networks, tumor-derived MV contribute to tumor escape, while DC-derived MV drive and regulate immune response.