Epitope cell surface

The path that leads from full sized protein to epitopes at the cell surface is complex, consisting of the generation of small peptides, translocation of the peptides to the endoplasmic reticulum by a transporter complex, loading of the peptides onto MHC class-I molecules and relocation of the MHC class-I-peptide complex to the cell surface (Rock and Goldberg, 1999). Since many of these steps are known to be prime targets for viral evasion strategies, the next step was to identify at what point the GAr interferes with the presentation of EBNAl. 

A simple protocol detailed in this chapter was established to develop RNA aptamers that bind to the electric organ nAChR and that are displaced by cocaine (8) (see Fig. 1 for a scheme). This protocol can be easily transferred to SELEX applications with other receptors or cell-surface epitopes, given that these are enriched in membrane preparations. 

Tissue Distribution of Biopharmaceuticals. By design, monoclonal antibodies exhibit high-afflnity binding to speciflc antigenic epitopes. These epitopes are present somewhere in the body perhaps on cell surfaces in healthy or cancerous tissue. In an ideal situation, a monoclonal... 

Jemmerson, R., and Agre, M. (1987) Monoclonal antibodies to different epitopes on a cell-surface enzyme, human placental alkaline phosphatase, effect different patterns of labeling with protein A—colloidal gold./. Histochem. Cytochem. 35,1277—1284. 

That heat is not the only method to unmask epitopes is exemplified by enzyme digestion or detergent treatment. The exact mechanism responsible for epitope retrieval with ultrasound is not clear, although intense heat is produced for an exceedingly short duration. It is known, however, that ultrasound and/or heat decreases the amount of negative charges on the cell surface (Joshi et al., 1983 Adler et al., 1988). Mechanical vibrations of molecules caused by ultrasound and heat are thought to unfold the protein molecule and to expose the epitopes. 

The Gal(al-3) Gal epitop is found on cell surfaces of many mammalians and New World monkeys, but not in humans, primates or Old World monkeys. In human blood up to 1 % of the circulating IgG molecules are directed against this epitop [30,44] presenting an enormous immunological barrier for xenotransplantation of animal organs (e.g. from pig) to humans. 

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