shrink in size in 70 percent of the patients and to completely disappear in 50 percent within days after a single infusion, with minimal or no side effects. The antibodies were designed to bind to a protein that is found only on the surface of cancerous B-cells and not on any other types of cells.

Monitoring: To follow the progress of a disease or treatment, surgeons can join radioactive isotopes to mAbs, subsequently using detectors to find the location of the radioisotope in the body. For example, this technique can be used to tell surgeons precisely where blood clots or cancer tumors are located.

Autopsies: Pathologists can determine quickly and accurately whether rabies virus, for example, is present in the brain of an animal by adding mAbs that seek out the virus.

Drug purification: Pure chemicals can be cheaply extracted from complex mixtures by adding mAbs that attach only to the chemical molecules wanted. Valuable chemicals present in even a very tiny percentage of the mixture can be separated and purified in this way. For example, this technique helped make interferon widely available.

Screening: To match tissues for transplant operations, doctors can use mAbs to search donor organs for antigens identical to those found in the patient. The process reveals which organs are most similar to the patient's own.

The development and production of mAbs have barely begun to bloom but cutting-edge researchers are already proclaiming the next advance in technology. The