IMMUNITY

There are four ways to acquire specific immunity: active natural, active artificial, passive natural, and passive artificial. Natural and artificial refer to the method of exposure. Natural exposure implies that contact with antigen or antibody (protein found in the plasma is responsible for humoral immunity) occurrs as part of everyday living and was not deliberate. Artificial exposure, also called immunization, is a deliberate introduction of antigen or antibody into the body.

"Active" and "passive" describe whose immune system is responding to the antigen (antigens are large molecules that stimulate a specific immune system response). When the individual is exposed to the antigen (either naturally or artificially), there can be a specific immune system response, which is called active immunity because the individual's own immune system is the cause of the immunity. Passive immunity occurs when another person or animal develops immunity and the immunity is transferred to a nonimmune individual.

Active natural immunity results from natural exposure to an antigen. Because the individual is not immune during the first exposure, he/she usually develops the symptoms of the disease. Interestingly, exposure to an antigen does not always produce symptoms. In active artificial immunity an antigen is deliberately introduced into an individual to stimulate his/her immune system. This process is vaccination, and the introduced antigen is vaccine. Injection of the vaccine is the usual mode of administration (tetanus toxoid, diphtheria, and whooping cough), although ingestion (Sabin poliomyelitis vaccine) is sometimes used. Passive natural immunity results from transfer of antibodies from a mother to her fetus or baby. Achieving passive artificial immunity usually begins with vaccinating an animal such as a horse. After the animal's immune system responds to the antigen, antibodies are removed from the animal and are injected into the individual requiring immunity.

AIDS

Acquired Immunodeficiency Syndrome (AIDS) is an immune deficient state caused by human immunodeficiency virus (HIV). AIDS was first reported in 1981. HIV is transmitted from an infected to a noninfected person by transfer of body fluids (e.g., blood, semen, vaginal secretions, breast milk) containing the virus. The major methods of transmission are sexual contact, contaminated needles used by intravenous drug users, and blood products.

Once infected with HIV, most people have no symptoms and no indication that they are infected. However infected individuals are able to transmit the virus to others. The signs and symptoms of AIDS are the following: persisted unexplained fatigue, soaking night sweats, shaking chill or fever lasting for several weeks, unexplained weight loss, swelling of lymph nodes which persists more than 3 months, chronic diarrhea, headaches, persistent dry cough and shortness of breath, white spots or unusual blemishes on the tongue or in the mouth, difficulties with speech, memory, concentration, or coordination.

If your immune system is healthy, white blood cells and antibodies help to fight against microscopic germs to keep you free from disease. When a foreign organism enters the body, it is attacked and destroyed.This response is coordinated by T-cell lymphocytes.

Most persons with AIDS develop pneumonia or a skin cancer. Approximately a third develops nervous system diseases, which include viral, fungal, or bacterial infections that cause meningitis (inflammation of the meninges), encephalitis, or myelitis (inflammation of the spinal cord). Other diseases of nervous system that occur in association with AIDS include parasitic cysts in the brain, abnormal growth of lymphoid tumors in the nervous system, and progressive form of dementia.

AIDS is a worldwide pandemic. At the beginning of 1996, scientists determined that more than 20 million people worldwide were infected with HIV and that more than 4.5 million people had AIDS. The WHO estimated that by the year 2000, more than 40 million people worldwide had been HIV-positive.

There are three main types of medications for HIV and AIDS. They are antiviral drugs, immune system boosters, and medications to help prevent or treat opportunistic infections. But the effectiveness of standard treatments is limited by the state of immunodeficiency. Researches on treatment are very active and new medications are being tested.The best way to fight AIDS is through education, awareness, and avoiding behaviors that may transmit HIV. Learning the facts about HIV and AIDS is the best protection.