Antibody production in transgenic plants.

Introduction In recent years, methods have been developed for the expression of immunoglobulin-encoding genes in a wide range of heterologous organisms, including non-lymphoid mammalian cells, insect cells, yeast, bacteria and plants. The isolation of antibodyencoding genes from hybridoma cells and their expression in these heterologous hosts has led to a revolution in monoclonal antibody technology, in which recombinant DNA techniques have been used to alter the structure, properties, specificity, function and immunogenicity of antibodies. Developments in recombinant antibody (recAb) engineering and recAb gene expression in heterologous systems have extended so far that it is now possible to express entire immune repertoires on bacteriophage surfaces [ 11. Once displayed on phage surfaces, specific antibodies can be isolated and improved by mutation in processes that mimic immune selection. These methodologies by-pass hybridoma technology and even immunization [ 11. The relative ease with which specific antibody-encoding genes can be isolated and expressed in heterologous systems has opened up a vast array of applications of recAb technology. As far as plant expression of antibodies (‘plantibodies’) is concerned, these applications can be broadly divided into two categories. Firstly, crop plants may be used for the large-scale production of commercially valuable antibodies, a process known as antibody farming. Secondly, antibodies may be produced in plant cells such that the activity, function or mobility of the cognate antigen may be modified in the expressing cells, a phenomenon called immunomodulation. Both types of applications require that functional, antigen-binding antibodies be able to accumulate in appropriate cellular compartments.