For example, the cytokine branch, which stimulates other immune system branches, includes the interleukins, interferons and colony-stimulating factors-all of which are proteins. Because of biotechnology, these proteins can now be produced in sufficient quantities to be marketed as therapeutics. Small doses of interleukin-2 have been effective in treating various cancers and AIDS, while interleukin-12 has shown promise in treating infectious diseases such as malaria and tuberculosis.
Researchers can also increase the number of a specific type of cell, with a highly specific function, from the cellular branch of the immune system. Under certain conditions, the immune system may not produce enough of the cell type a patient needs. Cell culture and natural growth factors that stimulate cell division allow researchers to provide or help the body create the needed cell type.
Cancer vaccines that help the immune system find and kill tumors have also shown therapeutic potential. Unlike other vaccines, cancer vaccines are given after the patient has the disease, so they are not preventative. They work by intensifying the reactions between the immune system and tumor. Despite many years of research, cancer vaccines have not yet emerged as a viable strategy to fight cancer. Nonetheless, researchers are optimistic that this kind of approach to battling cancer would be a major improvement over the therapies used today.
SUPPRESSING THE IMMUNE SYSTEM
In organ-transplant rejections and autoimmune diseases, suppressing our immune system is in our best interest. Currently we are using monoclonal antibodies to suppress, very selectively, the type of cell in the immune system responsible for organ-transplant rejection and autoimmune diseases, such as rheumatoid arthritis and multiple sclerosis. Patients given a biotechnology-based therapeutic often show significantly less transplant rejection than those given cyclosporin, a medicine that suppresses all immune function and leaves organ-transplant patients vulnerable to infection.
Inflammation, another potentially destructive immune system response, can cause diseases, such as ulcerative colitis. Two cytokines, interleukin-1 and tumor necrosis factor, stimulate the inflammatory response, so a number of biotechnology companies are investigating therapeutic compounds that block the actions or decrease production of these cytokines.
Organ transplantation provides an especially effective treatment for severe, life-threatening diseases of the heart, kidney and other organs. According to the United Network of Organ Sharing (UNOS), in the United States more than 92,000 people were on organ waiting lists as of May 19, 2006.
Organs and cells from other species-pigs and other animals-may be promising sources of donor organs and therapeutic cells. This concept is called xenotransplantation.
The most significant obstacle to xenotransplantation is the immune system's self-protective response. When nonhuman tissue is introduced into the body, the body cuts off blood flow to the donated organ. The most promising method for overcoming this rejection may be various types of genetic modification. One approach deletes the pig gene for the enzyme that is the main cause of rejection; another adds human genetic material to disguise the pig cells as human cells.
The potential spread of infectious disease from other species to humans through xenotransplantation needs close attention. However, a 1999 study of 160 people who had received pig cells as part of treatments showed no signs of ill health related to this exposure. In addition, scientists have succeeded at deleting the gene that triggers immune activity from a type of pig that cannot be infected with the virus that causes the most concern.
USING BIOPOLYMERS AS MEDICAL DEVICES
Nature has also provided us with biological molecules that can serve as useful medical devices or provide novel methods for drug delivery. Because they are more compatible with our tissues and our bodies absorb them when their job is done, they are superior to most man-made medical devices or delivery mechanisms.
For example, hyaluronate, a carbohydrate produced by a number of organisms, is an elastic, water-soluble biomolecule that is being used to prevent postsurgical scarring in cataract surgery, alleviate pain and improve joint mobility in patients with osteoarthritis and inhibit adherence of platelets and cells to medical devices, such as stents and catheters. A gel made of a polymer found in the matrix connecting our cells promotes healing in burn victims. Gauze-like mats made of long threads of fibrinogen, the protein that triggers blood clotting, can be used to stop bleeding in emergency situations. Adhesive proteins from living organisms are replacing sutures and staples for closing wounds. They set quickly, produce strong bonds, and are absorbed.
In the future, our individual genetic information will be used to prevent disease, choose medicines and make other critical decisions about health. This is personalized medicine, and it could revolutionize healthcare, making it safer, more cost-effective and, most importantly, more clinically effective.
Pharmacogenomics is a key term, referring to the use of information about the genome to develop drugs. Pharmacogenetics is also used to describe the study of the ways genomic variations affect drug responses.