[Principles, possibilities and limits of gene therapy].

The term gene therapy summarizes the attempts to correct inherited or acquired genetic defects by molecular genetic techniques. The manipulation of somatic cells differs in fundamental ethical aspects from that of germ cells. Some technical aspects of gene transfer, integration, and expression are discussed as well as the conditions set by the nature of the defect to be corrected. Adenosine deaminase deficiency is used as an example to demonstrate current approaches and their limitations.