The Target Cell

The target of a mAb must be as unique as possible for the disease to be treated. 

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The term endocrine disrupter (ED) has tended to be used for those chemicals which act specifically at the level of the hormone receptor present in the target cells of various organs. Such chemicals may either mimic the action of the natural hormone (agonistic activity) or are sufficiently similar in molecular shape to the naturally produced hormone to interfere with the interaction between the hormone and receptor, thus blocking or impeding the activation of the receptor (antagonsitic activity). Such effects may occur at very low concentrations (as with the endogenous hormone), compared with the concentrations normally required to elicit the more traditional toxic effects attributed to chemicals. Recently,... 

An important safety issue of viral vectors is whether or not the recombinant viruses are able to replicate in the infected cells. Replication of viral vectors is unwanted in most gene-therapy approaches. Therefore, replication-defective vectors have been designed, which are able to perform only one initial infectious cycle within the target cell. In addition, replication-competent vectors have been designed, which are able to productively infect the target cell and to spread in the target tissue. 

The known beneficial effects of retinoids on malignancies are assumed to relate to retinoid receptor-mediated antipromoting and anti-initiating effects. The latter appeals to be influenced by interference of several xenobiotics with different steps of the retinoid metabolism in the target cell. Of the carotenoids, (3-carotene is the most potent retinol precursor, yet being... 

Kleimnan et al. 2008). In addition, synthetic siRNAs are also subject to degradation in vivo by nuclease activity. Besides side effects and instability, the efficient and specific delivery of the RNAi indncers to the target cell still requires optimization. Here we snmmarize the cnrrent statns of nncleic acid-based antiviral therapentics. The focns will be on antiviral strategies nsing antisense and RNAi technology. Additionally, antiviral ribozymes and aptamers will be discussed briefly, with a focus on recent studies. Gene therapy approaches and delivery systems are the subject of Chapter 11 of this book. 

Fig. 1 Antiviral genes inhibit virus replication at different stages of the viral life cycle. Early inhibitors prevent the establishment of the viral genome in the target cell (class I, e.g., entry inhibitors, RT inhibitors for HIV). Intermediate inhibitors prevent viral gene expression or amplification of the viral genome (class II, e.g., siRNAs, antisense RNAs). Late inhibitors prevent virion assembly or release, or inactivate the mature virions (class III, e.g., transdominant core proteins, capsid-targeted virion inactivation, CTVI). A list of antiviral genes in each class is found in Table 1...

Several factors determine the response of a target cell to a hormone. These can be thought of in two general ways (1) as factors that affect the concentration of the hormone at the target cell (see Table 42—1) and (2) as factors that affect the acmal response of the target cell to the hormone (see Table 42—2). 

The metabolism (activation or inactivation) of the hormone in the target cell. 

The presence of a specific receptor defines the target cells for a given hormone. 

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