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Exosomes are membrane lipid vesicles in density at 1.13~1.21g/ml. These vesicles are released by numerous cells such as B lymphocytes, mastocytes, immature DCs, platelets, cytotoxic T lymphocytes, fibroblasts, epithelial cells, and tumor cells. Exosomes originate from late endosomes with membrane, i.e. multivesiclear bodies(MVB) and form by inward budding from the limiting membrand of MVBs into the endosomal lumen. Exosomes accumulate inside MVBs and can be released in the extracellular milieu following fusion of the external membrane of MVBs with plasma membrane. Exosomes can be defined according to morphological, biochemical and purification process criteria.Tumor cell can also secrete exosomes. Exosomes, in addition, can be separated from ascites of the patients with malignant tumors. Some researchers presumed and proved that they are secreted by tumor cells. Tumour-derived exosomes can be utilised as a source of tumour antigen for cross-priming to T-cells for CTL effect and are thus of interest for use in anti-tumour immunotherapy. The composition of exosomes are as follows: ① molecules associated with antigen presentation: MHC class I molecule, MHC class II molecule, HSC70 and HSP70. ② molecules associated with immune adhesion and signal transduction: ICAM-1, CD58, CD9, CD86/B7.2, Mac-1, MFG-E8 and so on. ③ other functional proteins: Annexin II ,TfR, CD55, CD59, Gi2 and so on. Exosomes, therefore, may be in possession of CTL effect, immune regulation, inducing apoptosis immune enduring and so on. The advantage of exosomes in cancer therapy are non-cell character, being freezed for storage, high stability, being seperated according to GMP criterion, little size and easy to be eliminated.At present, it is rare that exosomes derived from ascites of patients withDepartment o/Gynecology and Obstetrics, Xijing Hospital, FMMU
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