Understanding The Immune System

Immunotoxins Antibodies targeted against cancer cells can be coupled with drugs or radioactive substances, which they deliver directly to the cancer cell.

modifiers. Among these are interferons (now obtained through genetic engineering), interleukins, and thymus extracts. In some cases biological response modifiers are injected directly into the patient; in other cases they are used in the laboratory to transform some of the patient's own lymphocytes into tumor-hungry cells known as lymphokine-activated killer (LAK) cells, which are then injected back into the patient.

The Immune System and the Nervous System

A new field of research, known as psychoneuroimmunology is exploring how the immune system and the brain may interact to influence health. For years stress has been suspected of increasing susceptibility to various infectious diseases or cancer. Now evidence is mounting that the immune system and the nervous system are inextricably interconnected. Research has shown that a wide range of stresses, from losing a spouse to facing a tough examination, can deplete immune resources. In such studies, stress has caused levels of B and T cells to drop, natural killer cells to become less responsive, and fewer IgA antibodies to be secreted in the saliva. Students struggling to keep up with academic demands were found to be more likely than their less pressured peers to succumb to infectious mononucleosis or oral herpes infections. Experimental animals subjected to stress were usually less able to resist disease-unless they were able to take actions to control the stress. Some animals have even been "taught" through behavioral conditioning to produce certain immune responses. Biological links between the immune system and the central nervous system exist at several levels. One well-known pathway involves the adrenal glands, which, in response to stress messages from the brain, release corticosteroid hormones into the blood. In addition to helping a person respond to emergencies by mobilizing the body's energy reserves, these "stress hormones" decrease antibodies and reduce lymphocytes in both number and strength.