Earth Science: Immune System Human – Immune Response to Disease
Harmful bacteria, viruses, and other materials are constantly present in the environment and can cause illness and disease. To protect itself, the human body uses its immune system.
The role of the immune system is to recognize defective and foreign cells and combat them using both specific and non-specific defensive strategies. The first line of defense is a series of nonspecific innate (passive) defenses. For example, the skin and mucous membrane coatings of the digestive, respiratory, and genital tracts have chemical defenses against most bacteria, viruses, and parasites.
The skin’s dead surface cells and the oils produced by the sebaceous glands form an effective barrier against many dangerous microbes. Other harmful bacteria are stopped by the enzymes and antibacterial proteins secreted by the mucous membranes.
The specific defense mechanisms (the active or acquired response) of the immune system are triggered when special cells, lymphocytes called B-cells and T-cells, recognize individual antigens on the surface of the invading cells as foreign. When infection does occur, antibodies are formed to mount a defense targeted to the specific pathogen.
The invading cells are attacked and consumed by white blood cells called macrophages. Inflammation and fever associated with infections increase the production and release of the defending macrophages, thus hastening the body’s recovery.
Primary infection
A primary infection occurs when an infectious organism enters a body for the first time. In response, the pathogen is isolated by an immune cell and broken into pieces displayed on the immune cell surface. This stimulates the production of specific defensive cells.
The defensive cells try to consume the invaders through phagocytosis or kill them with superoxides. The immune system learns to recognize a pathogen by the chemicals it produces or the protein markers (anti- gens) on its surface. The immune system then produces antibodies that cling to the invaders.
After a primary infection, antibodies and memory cells remain to help the immune system recognize and efficiently combat a new infection by the same pathogen.
AIDS
AIDS (Acquired Immune Deficiency Syndrome) is a disease caused by the human immune deficiency virus (HIV). HIV is spread in body fluids such as blood, sperm, vaginal secretions, and mother’s breast milk.
Researchers are hunting for a cure; none has yet been found. Preventing infection, especially through protected sex, is the best defense against AIDS
BASICS
VACCINATION pro vides protection against specific diseases. In active immunization, weakened infectious cells are used to trigger the production of antibodies.
With passive immunization, a serum with the needed antibodies is administered