Assembly and plasma membrane targeting of recombinant immunoglobulin chains in plants with a murine immunoglobulin transmembrane sequence

The cDNA encoding a full-length murine immunoglobulin yl heavy chain with i ts native leader sequence, transmembrane and intracellular domains was intr oduced into transgenic plants. Transformed plants expressed the recombinant polypeptide, but, in contrast to plants expressing the heavy chain without transmembrane sequence, the protein appeared to be associated with a plant cell membrane. Extraction of the membrane-associated heavy chain required the presence of a non-ionic detergent, and immunofluorescence studies of pr otoplasts demonstrated surface expression of membrane Ig heavy chain on up to 40% of the cells from a transgenic leaf. In plants expressing both the m embrane Ig heavy chain and its partner light chain, functional antibody was also localised to the plant cell membrane and retention of the heavy chain at this site appeared to have no effect on the efficiency of antibody asse mbly. This approach of localising and accumulating recombinant antibody in cell membranes may have a number of applications, including passive immunis ation against plant pathogens.