Exosomal Markers

Exosomes are the most extensively researched type of extracellular vesicle. Extracellular vesicles mediate inter-cellular (between cell) communication via the transmission of molecules to both local and distant recipient cells. Other types of extracellular vesicle include apoptotic extracellular vesicles (apoptotic bodies) and ectosomes, which are distinguished based on size and the nature of their biogenesis. Exosomes are lipid bilayer enclosed vesicles of 30-150nm in diameter that appear spheroid in solution under transmission electron microscopy. Exosomes contain bioactive cargo such as lipids, proteins and nucleic acids including microRNA. Due to the presence of a lipid bilayer, the contents of exosomes escape immune surveillance and avoid rapid degradation. Exosomes are formed within endosomes from the inward budding of the endosomal membrane to generate intraluminal vesicles (ILVs) within multivesicular endosomes. Multivesicular endosomes subsequently fuse with the plasma membrane giving rise to exosome release, which is mediated by the Rab family of small GTPases. Alternatively, multivesicular endosomes can be directed to lysosomes for degradation precluding exosome release. The process of inward budding of the endosomal membrane during exosome formation results in the reorientation of endocytosed trans-membrane proteins such that they are signalling competent upon exosome release. Following secretion from the donor cell exosomes fuse with the plasma membrane of a recipient cell where their cargo is delivered. The receptors and cell surface molecules expressed on the exosomal membranes are likely to play a role in specific cellular uptake. Exosomes reflect the biological characteristics of their donor cells, but are characterised by the presence of tetraspanins (CD81, CD82, CD9, CD63), apoptosis linked gene 2 interacting protein X (ALIX), tumor susceptibility gene 101 (TSG101), endosomal sorting complex required for transport (ESCRT), cytoskeletal proteins and heat shock proteins. Thus, these exosomal proteins serve as useful general markers for detection. Of note, ESCRT, TSG101 and ALIX are all implicated in the formation of ILVs and hence the production of exosomes. Exosomes are released by virtually all eukaryotic cells and are present in many biological fluids such as urine, amniotic fluid, bronchoalveolar lavage fluid, breast milk, saliva, cerebrospinal fluid and blood. The functions of exosomes are varied and include the maintenance of many normal physiological processes. Aberrant exosomal signalling has been implicated in diseases such as cancer, cardiovascular disease, immunological and neurological disorders and the transfer of infectious particles. Moreover, exosomes have become a focal point of research as they hold great promise as diagnostic tools or as putative vehicles for drug delivery. We offer a wide range of exosomal markers including CD81 antibodies, CD9 antibodies, CD82 antibodies, HSC70 antibodies, and CD63 antibodies, covering numerous host species, clonalities, formulations, and validated applications.