Recent advances in the field of recombinant antibodies have permitted the manipulation of genes encoding specific antibodies, thus allowing their ectopic expression in a wide variety of non-lymphoid cells. This volume describes how the ectopic expression of antibodies, as secreted or as intracellularly retargeted molecules, can be exploited to block biological functions or to confer new phenotypic traits (e.g. resistance to a virus). This is the first book describing this emerging technology, which is receiving increasing attention for application in many different fields and biological systems - from human gene therapy to plant biotechnology.