Gene splicing (develop) as a new technique that may (revolutionize) medical treatment in the next century. Although the technique is still experimental, it (emerge) as an important development in both immunization and treatment. In a few years, we may be able to (immunize) easily against a whole number of dangerous viral diseases. Here is how the technique (work). Genes of dangerous viruses (split), and portions of the virus DNA (attach) to other harmless cells such as blood cells or bone marrow cells. When these altered cells (inject) into the body, they will be able to (reproduce) in sufficient quantities so that an immune reaction (occur). The harmless cells (appear) so similar to the virus cells that the immune system (produce) various antibodies against these artificial cells. These antibodies also (attack) the real virus cells because the chromosome structures of the two kinds of cells (seem) nearly identical to the antibodies. This technique will enable scientists to make vaccines against a whole variety of diseases that are presently too virulent to (use) to produce vaccines for human use.