Transgenic animals and the study of the immune system

Transgenic technology, the introduction of genetic information into the germ line of an animal to alter its genetic constitution stably, provides a powerful tool for studying the development, functions, and malfunctions of complex biological systems. The main advantage has been that it is possible to study the gene functioning in its natural milieu. This is particularly informative when the genes have been manipulated such that the regulation and tissue specificity of expression are altered. Although transgenic animals bear the introduced gene in every tissue, expression of that gene may be widespread or directed to particular cell lineages, depending on the regulatory sequences chosen.