Immune System : Nervous System, Gene Therapy

by National Institute of Health

(Page 6 of 6)

The Immune System and the Nervous System

Evidence is mounting that the immune system and the nervous system are linked in several ways. One well-known connection involves the adrenal glands. In response to stress messages from the brain, the adrenal glands release hormones into the blood. In addition to helping a person respond to emergencies by mobilizing the body's energy reserves, these "stress hormones" can stifle the protective effects of antibodies and lymphocytes.

Hormones and other chemicals known to convey messages among nerve cells have been found to "speak" to cells of the immune system. Indeed, some immune cells are able to manufacture typical nerve cell products, while some lymphokines can transmit information to the nervous system. What's more, the brain may send messages directly down nerve cells to the immune system. Networks of nerve fibers have been found connecting to the lymphoid organs.

Frontiers in Immunology

Scientists are now able to mass-produce immune cell secretions, both antibodies and lymphokines, as well as specialized immune cells. The ready supply of these materials not only has revolutionized the study of the immune system itself but also has had an enormous impact on medicine, agriculture, and industry.

Monoclonal antibodies are identical antibodies made by the many descendants (clones) of a single B cell. Because of their unique specificity for different molecules, monoclonal antibodies are promising treatments for a range of diseases. Researchers make monoclonal antibodies by injecting a mouse with a target antigen and then fusing B cells from the mouse with another long-lived cell. The resulting hybrid cell becomes a type of antibody factory, turning out identical copies of antibody molecules specific for the target antigen.

Mouse antibodies are "foreign" to people, however, and might trigger their own immune response when injected into a human. Therefore, researchers have begun to study "humanized" monoclonal antibodies. To construct these molecules, scientists take the antigen-binding portion of a mouse antibody and attach it to a human antibody scaffolding, greatly reducing the foreign portion of the molecule.

Because they recognize very specific molecules, monoclonal antibodies are used in diagnostic tests to identify invading pathogens or changes in the body's proteins. In medicine, monoclonal antibodies can attach to cancer cells, blocking the chemical growth signals that cause the cells to divide out of control. In other cases, monoclonal antibodies can carry potent toxins into select cells, killing the cell while leaving its neighbors untouched.

Genetic Engineering

Genetic engineering allows scientists to pluck genes - segments of the hereditary material, DNA - from one type of organism and combine them with genes of a second organism. In this way relatively simple organisms such as bacteria or yeast can be induced to make quantities of human proteins, including hormones such as insulin as well as lymphokines and monokines. They can also manufacture proteins from infectious agents, such as the hepatitis virus or HIV, for use in vaccines.

Gene Therapy

Genetic engineering also holds promise for gene therapy - replacing altered or missing genes or adding helpful genes. Severe combined immunodeficiency disease is a prime candidate for gene therapy. SCID is caused by the lack of an enzyme due to a single missing gene. A genetically engineered version of the missing gene can be introduced into cells taken from the patient's bone marrow. After treated marrow cells begin to produce the enzyme, they can be injected back into the patient.

Cancer is another target for gene therapy. In pioneering experiments, scientists are removing cancer-fighting lymphocytes from the cancer patient's tumor, inserting a gene that boosts the lymphocytes' ability to make quantities of a natural anticancer product, then growing the restructured cells in quantity in the laboratory. These cells are injected back into the patient, where they can seek out the tumor and deliver large doses of the anticancer chemical.

Immunoregulation

Research into the delicate checks and balances that control the immune response is increasing knowledge of normal and abnormal immune functions. Someday it may be possible to treat diseases such as systemic lupus erythematosus by suppressing parts of the immune system that are overactive. By transplanting immature human immune tissues or immune cells into SCID mice, scientists have created a living model of the human immune system. This animal model promises to be immensely valuable in helping scientists understand the immune system and manipulate it benefit human health.

Summary

Although scientists have learned much about the immune system, they continue to study how the body launches attacks that destroy invading microbes, infected cells, and tumors while ignoring healthy tissues. New technologies for identifying individual immune cells are now letting scientists quickly determine which targets are triggering an immune response. Improvements in microscopy are permitting the first-ever observations of B cells, T cells, and other cells as they interact within lymph nodes and other body tissues.

In addition, scientists are rapidly unraveling the genetic blueprints that direct the human immune response as well as those that dictate the biology of bacteria, viruses, and parasites. The combination of new technology and expanded genetic information will no doubt teach us even more about how the body protects itself from disease.

About the Author

NIH is the nation's medical research agency - making important medical discoveries that improve health and save lives. The National Institutes of Health (NIH), a part of the U.S. Department of Health and Human Services, is the primary Federal agency for conducting and supporting medical research.